Stone_Red/naming-convention
1
0
Fork 0
mirror of https://github.com/Stone-Red-Code/naming-convention.git synced 2026-09-04 00:56:16 +02:00
Code Issues Packages Projects Releases Wiki Activity
Files
master
naming-convention/SQL Server Name Convention and T-SQL Programming Style.md
T

765 lines
63 KiB
Markdown
Raw Permalink Blame History

This file contains ambiguous Unicode characters
This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.
# SQL Server Name Convention and T-SQL Programming Style
> There are only two hard things in Computer Science: cache invalidation and naming things
> -- <cite>[Phil Karlton](https://www.karlton.org/2017/12/naming-things-hard/)</cite>
[Naming convention](https://en.wikipedia.org/wiki/Naming_convention_(programming)) is a set of rules for choosing the character sequence to be used for identifiers which denote variables, types, functions, and other entities in source code and documentation.
Reasons for using a naming convention (as opposed to allowing programmers to choose any character sequence) include the following:
- To reduce the effort needed to read and understand source code.
- To enable code reviews to focus on more important issues than arguing over syntax and naming standards.
- To enable code quality review tools to focus their reporting mainly on significant issues other than syntax and style preferences.
## Table of Contents
- [SQL Server Object Name Convention](#sql-server-object-name-convention)
- [SQL Server Data Types Recommendation](#data-types-recommendation)
- [SQL Server Function Recommendations](#function-recommendation)
- [T-SQL Programming T-SQL Style](#t-sql-programming-style)
- [General T-SQL programming style](#general-t-sql-programming-style)
- [Stored procedures and functions programming style](#programming-style)
- [Dynamic T-SQL Recommendation](#dynamic-t-sql-recommendation)
- [Reference and useful links](#reference)
<a id="sql-server-object-name-convention"></a>
## SQL Server Object Name Convention
| Object | Code | Notation | Length | Plural | Prefix | Suffix | Abbreviation | Char Mask | Example |
|------------------------------------------|------| ---------- |-------:|--------|---------|--------|--------------|--------------|--------------------------------------|
| [Database] | | UPPERCASE | 30 | No | No | No | Yes | [A-z] | `MYDATABASE` |
| [Schema] | | lowercase | 30 | No | No | No | Yes | [a-z][0-9] | `myschema` |
| [Global Temporary Table] | | PascalCase | 117 | No | No | No | Yes | ##[A-z][0-9] | `##MyTable` |
| [Local Temporary Table] | | PascalCase | 116 | No | No | No | Yes | #[A-z][0-9] | `#MyTable` |
| [File Table] | | PascalCase | 128 | No | `FT_` | No | Yes | [A-z][0-9] | `FT_MyTable` |
| [Memory-optimized SCHEMA_AND_DATA Table] | | PascalCase | 128 | No | `MT_` | `_SD` | Yes | [A-z][0-9] | `MT_MyTable_SD` |
| [Memory-optimized SCHEMA_ONLY Table] | | PascalCase | 128 | No | `MT_` | `_SO` | Yes | [A-z][0-9] | `MT_MyTable_SO` |
| [Temporal Table] | | PascalCase | 128 | No | No | `_TT` | Yes | [A-z][0-9] | `MyTable_TT` |
| [Disk-Based Table] | U | PascalCase | 128 | No | No | No | Yes | [A-z][0-9] | `MyTable` |
| [Disk-Based Wide Table - SPARSE Column] | U | PascalCase | 128 | No | No | `_SPR` | Yes | [A-z][0-9] | `MyTable_SPR` |
| [Table Column] | | PascalCase | 128 | No | No | No | Yes | [A-z][0-9] | `MyColumn` |
| [Table Column SPARSE] | | PascalCase | 128 | No | No | `_SPR` | Yes | [A-z][0-9] | `MyColumn_SPR` |
| [Columns Check Constraint] | C | PascalCase | 128 | No | `CTK_` | No | Yes | [A-z][0-9] | `CTK_MyTable_MyColumn_AnotherColumn` |
| [Column Check Constraint] | C | PascalCase | 128 | No | `CK_` | No | Yes | [A-z][0-9] | `CK_MyTable_MyColumn` |
| [Column Default Values] | D | PascalCase | 128 | No | `DF_` | No | Yes | [A-z][0-9] | `DF_MyTable_MyColumn` |
| [Table Primary Key] | PK | PascalCase | 128 | No | `PK_` | No | Yes | [A-z][0-9] | `PK_MyTableID` |
| [Table Unique (Alternative) Key] | UQ | PascalCase | 128 | No | `AK_` | No | Yes | [A-z][0-9] | `AK_MyTable_MyColumn_AnotherColumn` |
| [Table Foreign Key] | F | PascalCase | 128 | No | `FK_` | No | Yes | [A-z][0-9] | `FK_MyTable_ForeignTableID` |
| [Table Clustered Index] | | PascalCase | 128 | No | `IXC_` | No | Yes | [A-z][0-9] | `IXC_MyTable_MyColumn_AnotherColumn` |
| [Table Non Clustered Index] | | PascalCase | 128 | No | `IX_` | No | Yes | [A-z][0-9] | `IX_MyTable_MyColumn_AnotherColumn` |
| [DDL Trigger] | TR | PascalCase | 128 | No | `TR_` | `_DDL` | Yes | [A-z][0-9] | `TR_LogicalName_DDL` |
| [DML Trigger] | TR | PascalCase | 128 | No | `TR_` | `_DML` | Yes | [A-z][0-9] | `TR_MyTable_LogicalName_DML` |
| [Logon Trigger] | TR | PascalCase | 128 | No | `TR_` | `_LOG` | Yes | [A-z][0-9] | `TR_LogicalName_LOG` |
| [View] | V | PascalCase | 128 | No | `VI_` | No | No | [A-z][0-9] | `VI_LogicalName` |
| [Indexed View] | V | PascalCase | 128 | No | `VIX_` | No | No | [A-z][0-9] | `VIX_LogicalName` |
| [Statistic] | | PascalCase | 128 | No | `ST_` | No | No | [A-z][0-9] | `ST_MyTable_MyColumn_AnotherColumn` |
| [Stored Procedure] | P | PascalCase | 128 | No | `usp_` | No | No | [A-z][0-9] | `usp_LogicalName` |
| [Scalar User-Defined Function] | FN | PascalCase | 128 | No | `udf_` | No | No | [A-z][0-9] | `udf_FunctionLogicalName` |
| [Table-Valued Function] | FN | PascalCase | 128 | No | `tvf_` | No | No | [A-z][0-9] | `tvf_FunctionLogicalName` |
| [Synonym] | SN | camelCase | 128 | No | `sy_` | No | No | [A-z][0-9] | `sy_logicalName` |
| [Sequence] | SO | PascalCase | 128 | No | `sq_` | No | No | [A-z][0-9] | `sq_TableName` |
| [CLR Assembly] | | PascalCase | 128 | No | `CA ` | No | Yes | [A-z][0-9] | `CALogicalName` |
| [CLR Stored Procedures] | PC | PascalCase | 128 | No | `pc_` | No | Yes | [A-z][0-9] | `pc_CAName_LogicalName` |
| [CLR Scalar User-Defined Function] | | PascalCase | 128 | No | `cudf_` | No | No | [A-z][0-9] | `cudf_CAName_LogicalName` |
| [CLR Table-Valued Function] | | PascalCase | 128 | No | `ctvf_` | No | No | [A-z][0-9] | `ctvf_CAName_LogicalName` |
| [CLR User-Defined Aggregates] | | PascalCase | 128 | No | `ca_` | No | No | [A-z][0-9] | `ca_CAName_LogicalName` |
| [CLR User-Defined Types] | | PascalCase | 128 | No | `ct_` | No | No | [A-z][0-9] | `ct_CAName_LogicalName` |
| [CLR Triggers] | | PascalCase | 128 | No | `ctr_` | No | No | [A-z][0-9] | `ctr_CAName_LogicalName` |
| [Linked Server] | | PascalCase | 128 | No | `ls_` | No | No | [A-z][0-9] | `ls_LogicalName` |
[Database]:https://docs.microsoft.com/en-us/sql/t-sql/statements/create-database-transact-sql
[Schema]:https://docs.microsoft.com/en-us/sql/relational-databases/security/authentication-access/create-a-database-schema
[Global Temporary Table]:https://docs.microsoft.com/en-us/sql/relational-databases/tables/tables
[Local Temporary Table]:https://docs.microsoft.com/en-us/sql/relational-databases/tables/tables
[File Table]:https://docs.microsoft.com/en-us/sql/relational-databases/blob/filetables-sql-server
[Memory-optimized SCHEMA_AND_DATA Table]:https://docs.microsoft.com/en-us/sql/relational-databases/in-memory-oltp/introduction-to-memory-optimized-tables
[Memory-optimized SCHEMA_ONLY Table]:https://docs.microsoft.com/en-us/sql/relational-databases/in-memory-oltp/defining-durability-for-memory-optimized-objects
[Temporal Table]:https://docs.microsoft.com/en-us/sql/relational-databases/tables/temporal-tables
[Disk-Based Table]:https://docs.microsoft.com/en-us/sql/relational-databases/in-memory-oltp/comparing-disk-based-table-storage-to-memory-optimized-table-storage
[Disk-Based Wide Table - SPARSE Column]:https://docs.microsoft.com/en-us/sql/relational-databases/tables/tables#wide-tables
[Table Column]:https://docs.microsoft.com/en-us/sql/t-sql/statements/alter-table-transact-sql
[Table Column SPARSE]:https://docs.microsoft.com/en-us/sql/relational-databases/tables/use-sparse-columns
[Columns Check Constraint]:https://docs.microsoft.com/en-us/sql/relational-databases/tables/create-check-constraints
[Column Check Constraint]:https://docs.microsoft.com/en-us/sql/relational-databases/tables/create-check-constraints
[Column Default Values]:https://docs.microsoft.com/en-us/sql/relational-databases/tables/specify-default-values-for-columns
[Table Primary Key]:https://docs.microsoft.com/en-us/sql/relational-databases/tables/create-primary-keys
[Table Unique (Alternative) Key]:https://docs.microsoft.com/en-us/sql/relational-databases/tables/create-unique-constraints
[Table Foreign Key]:https://docs.microsoft.com/en-us/sql/relational-databases/tables/create-foreign-key-relationships
[Table Clustered Index]:https://docs.microsoft.com/en-us/sql/relational-databases/indexes/clustered-and-nonclustered-indexes-described
[Table Non Clustered Index]:https://docs.microsoft.com/en-us/sql/relational-databases/indexes/clustered-and-nonclustered-indexes-described
[DDL Trigger]:https://docs.microsoft.com/en-us/sql/t-sql/statements/create-trigger-transact-sql
[DML Trigger]:https://docs.microsoft.com/en-us/sql/relational-databases/triggers/dml-triggers
[Logon Trigger]:https://docs.microsoft.com/en-us/sql/t-sql/statements/create-trigger-transact-sql
[View]:https://docs.microsoft.com/en-us/sql/relational-databases/views/views
[Indexed View]:https://docs.microsoft.com/en-us/sql/relational-databases/views/create-indexed-views
[Statistic]:https://docs.microsoft.com/en-us/sql/t-sql/statements/create-statistics-transact-sql
[Stored Procedure]:https://docs.microsoft.com/en-us/sql/t-sql/statements/create-procedure-transact-sql
[Scalar User-Defined Function]:https://docs.microsoft.com/en-us/sql/relational-databases/user-defined-functions/create-user-defined-functions-database-engine#Scalar
[Table-Valued Function]:https://docs.microsoft.com/en-us/sql/relational-databases/user-defined-functions/create-user-defined-functions-database-engine#TVF
[Synonym]:https://docs.microsoft.com/en-us/sql/relational-databases/synonyms/synonyms-database-engine
[Sequence]:https://docs.microsoft.com/en-us/sql/relational-databases/sequence-numbers/sequence-numbers
[CLR Assembly]:https://docs.microsoft.com/en-us/sql/relational-databases/clr-integration/assemblies/creating-an-assembly
[CLR Stored Procedures]:https://docs.microsoft.com/en-us/dotnet/framework/data/adonet/sql/clr-stored-procedures
[CLR Scalar User-Defined Function]:https://docs.microsoft.com/en-us/sql/relational-databases/clr-integration-database-objects-user-defined-functions/clr-user-defined-functions
[CLR Table-Valued Function]:https://docs.microsoft.com/en-us/sql/relational-databases/clr-integration-database-objects-user-defined-functions/clr-table-valued-functions
[CLR User-Defined Aggregates]:https://docs.microsoft.com/en-us/sql/relational-databases/clr-integration-database-objects-user-defined-functions/clr-user-defined-aggregates
[CLR User-Defined Types]:https://docs.microsoft.com/en-us/sql/relational-databases/clr-integration-database-objects-user-defined-types/clr-user-defined-types
[CLR Triggers]:https://docs.microsoft.com/en-us/sql/relational-databases/triggers/create-clr-triggers
[Linked Server]:https://docs.microsoft.com/en-us/sql/relational-databases/linked-servers/linked-servers-database-engine
**[⬆ back to top](#table-of-contents)**
<a id="data-types-recommendation"></a>
## SQL Server Data Types Recommendation
More details about SQL Server data types and mapping it with another databases and program languages you can find [here](https://github.com/ktaranov/sqlserver-kit/blob/master/SQL%20Server%20Data%20Types.md)
| General Type | Type | ANSI | Recommended | What use instead | Why use or not |
|----------------------|---------------------|------|----------------|--------------------|------------------------------------------------------------------------------------|
| Exact Numerics | [bit] | No | *Maybe* | [tinyint][1] | `bit` convert any number (except 0) to 1, 0 converted to 0 |
| Exact Numerics | [tinyint][1] | No | *Maybe* | [int][1] | for saving 3 bytes compare to `int` data type or for replacing `bit` data type |
| Exact Numerics | [smallint][1] | Yes | *Maybe* | [int][1] | for saving 2 bytes compare to `int` data type |
| Exact Numerics | [int][1] | Yes | Yes | - | |
| Exact Numerics | [bigint][1] | No | Yes | [int][1] | if you work more than 2^31 numbers. |
| Exact Numerics | [decimal][2] | Yes | Yes | - | |
| Exact Numerics | [smallmoney][3] | No | *Maybe* | [decimal][2] | [possibility to loss precision due to rounding errors][9] |
| Exact Numerics | [money][3] | No | *Maybe* | [decimal][2] | [possibility to loss precision due to rounding errors][9] |
| Approximate Numerics | [real][4] | Yes | Yes | - | |
| Approximate Numerics | [float][4](1-24) | Yes | No | [real][4] | SQL Server automatically converts `float(1-24)` to `real` data type |
| Approximate Numerics | [float][4](24-53) | Yes | Yes | - | |
| Date and Time | [date] | Yes | Yes | - | |
| Date and Time | [smalldatetime] | No | *Maybe* | [date] | |
| Date and Time | [time] | Yes | Yes | - | |
| Date and Time | [datetime2] | No | Yes | - | |
| Date and Time | [datetime] | Yes | *Maybe* | [datetime2] | [On the Advantages of DateTime2(n) over DateTime] |
| Date and time | [datetimeoffset] | No | Yes | - | |
| Character Strings | [char][5] | Yes | *Maybe* | [varchar][5] | Save 1 byte from `varchar`, but be ready for trailing spaces |
| Character Strings | [varchar][5] | Yes | Yes | - | |
| Character Strings | [varchar(max)][5] | Yes | Yes | - | |
| Character Strings | [nchar][6] | Yes | *Maybe* | [nvarchar][6] | |
| Character Strings | [nvarchar][6] | Yes | Yes | - | |
| Character Strings | [nvarchar(max)][6] | Yes | Yes | - | |
| Character Strings | [ntext][7] | No | **Deprecated** | [nvarchar(max)][6] | [NVARCHAR(MAX) VS NTEXT in SQL Server] |
| Character Strings | [text][7] | No | **Deprecated** | [varchar(max)][6] | [Differences Between Sql Server TEXT and VARCHAR(MAX) Data Type] |
| Binary Strings | [image][7] | No | **Deprecated** | [varbinary(max)][8]| [VARBINARY(MAX) Tames the BLOB] |
| Binary Strings | [binary][8] | Yes | **Deprecated** | [varbinary][8] | [Conversions between any data type and the binary data types are not guaranteed][8]|
| Binary Strings | [varbinary][8] | Yes | Yes | - | |
| Binary Strings | [varbinary(max)][8] | Yes | Yes | - | |
| Other Data Types | [cursor] | No | Yes | - | |
| Other Data Types | [sql_variant] | No | Yes | - | |
| Other Data Types | [hierarchyid] | No | Yes | - | |
| Other Data Types | [rowversion] | No | *Maybe* | - | |
| Other Data Types | [timestamp] | No | **Deprecated** | [rowversion] | it is just synonym to [rowversion] data type and must be [removed][] |
| Other Data Types | [uniqueidentifier] | No | Yes | - | |
| Other Data Types | [xml] | Yes | Yes | - | |
| Other Data Types | [table] | No | *Maybe* | - | |
| Spatial Data Types | [geometry] | No | Yes | - | |
| Spatial Data Types | [geography] | No | Yes | - | |
[1]:https://docs.microsoft.com/sql/t-sql/data-types/int-bigint-smallint-and-tinyint-transact-sql
[2]:https://docs.microsoft.com/sql/t-sql/data-types/decimal-and-numeric-transact-sql
[3]:https://docs.microsoft.com/sql/t-sql/data-types/money-and-smallmoney-transact-sql
[4]:https://docs.microsoft.com/sql/t-sql/data-types/float-and-real-transact-sql
[5]:https://docs.microsoft.com/sql/t-sql/data-types/char-and-varchar-transact-sql
[6]:https://docs.microsoft.com/sql/t-sql/data-types/nchar-and-nvarchar-transact-sql
[7]:https://docs.microsoft.com/sql/t-sql/data-types/ntext-text-and-image-transact-sql
[8]:https://docs.microsoft.com/sql/t-sql/data-types/binary-and-varbinary-transact-sql
[9]:https://www.red-gate.com/hub/product-learning/sql-prompt/avoid-use-money-smallmoney-datatypes
[bit]:https://docs.microsoft.com/sql/t-sql/data-types/bit-transact-sql
[date]:https://docs.microsoft.com/sql/t-sql/data-types/date-transact-sql
[smalldatetime]:https://docs.microsoft.com/sql/t-sql/data-types/smalldatetime-transact-sql
[time]:https://docs.microsoft.com/sql/t-sql/data-types/time-transact-sql
[datetime2]:https://docs.microsoft.com/sql/t-sql/data-types/datetime2-transact-sql
[datetime]:https://docs.microsoft.com/sql/t-sql/data-types/datetime-transact-sql
[datetimeoffset]:https://docs.microsoft.com/sql/t-sql/data-types/datetimeoffset-transact-sql
[cursor]:https://docs.microsoft.com/sql/t-sql/data-types/cursor-transact-sql
[sql_variant]:https://docs.microsoft.com/sql/t-sql/data-types/sql-variant-transact-sql
[hierarchyid]:https://docs.microsoft.com/sql/t-sql/data-types/hierarchyid-data-type-method-reference
[rowversion]:https://docs.microsoft.com/sql/t-sql/data-types/rowversion-transact-sql
[timestamp]:https://docs.microsoft.com/sql/t-sql/data-types/rowversion-transact-sql#remarks
[uniqueidentifier]:https://docs.microsoft.com/sql/t-sql/data-types/uniqueidentifier-transact-sql
[xml]:https://docs.microsoft.com/sql/t-sql/xml/xml-transact-sql
[table]:https://docs.microsoft.com/sql/t-sql/data-types/table-transact-sql
[geometry]:https://docs.microsoft.com/sql/t-sql/spatial-geometry/spatial-types-geometry-transact-sql
[geography]:https://docs.microsoft.com/sql/t-sql/spatial-geography/spatial-types-geography
[On the Advantages of DateTime2(n) over DateTime]:http://www.sqltact.com/2012/12/on-advantages-of-datetime2n-over.html
[Differences Between Sql Server TEXT and VARCHAR(MAX) Data Type]:https://sqlhints.com/2016/05/11/differences-between-sql-server-text-and-varcharmax-data-type/
[NVARCHAR(MAX) VS NTEXT in SQL Server]:https://www.sqlservercurry.com/2010/07/nvarcharmax-vs-ntext-in-sql-server.html
[VARBINARY(MAX) Tames the BLOB]:https://www.itprotoday.com/microsoft-visual-studio/varbinarymax-tames-blob
[removed]:https://feedback.azure.com/forums/908035-sql-server/suggestions/32889865-deprecate-timestamp-the-keyword-not-rowversion-i
**[⬆ back to top](#table-of-contents)**
<a id="function-recommendation"></a>
## SQL Server Function Recommendations
This is only recommendations! But it is consistent for choosing only 1 function from possibles alterntives and use only it.
| Not Recommended | Recommended | When and Why | More details |
|-----------------|-----------------|------------------------------------------------------------------------------------------------------------------------------------------------|----------------|
| [`!=`][12] | [`<>`][12] | `<>` is [`ANSI`], `!=` not `ANSI`, [`<>` and `!=` are identical][13] | [13] |
| [`CONVERT`][10] | [`CAST`][10] | `CAST` is [`ANSI`] | [14],[15] |
| [`ISNULL`] | [`COALECSE`] | `COALECSE` is [`ANSI`] and supports more than two arguments, `ISNULL` has dangerous behaviour with possibility to implicit triming string | [16],[17] |
| [`DATEDIFF`] | [`DATEADD`] | The predicate `MyDateTime < DATEADD(SECOND, -1, GETUTCDATE())` syntax is [`SARGable`] | [18],[19] |
| [`SELECT`] | [`SET`] | Using `SET` (is [`ANSI`]) instead of `SELECT` when assigning variables due to properly work with `Msg 501 Subquery returned more than 1 value` | [20],[21],[22] |
| [`STR`] | [`CAST`][10] | `STR` is not [`ANSI`], extremly slow, don't use more than 15 digits, and has rounding problem - use `CAST` plus concatenate instead `STR` | [23] |
| [`ISNUMERIC`] | [`TRY_CONVERT`] | `ISNUMERIC` can often lead to data type conversion errors, when importing data. For SQL Server below 2012 use `WHERE` with `LIKE`. | [24] |
[12]:https://docs.microsoft.com/sql/t-sql/language-elements/comparison-operators-transact-sql
[13]:https://dba.stackexchange.com/a/155670/107045
[14]:https://www.sentryone.com/blog/aaronbertrand/backtobasics-cast-vs-convert
[15]:https://nakulvachhrajani.com/2011/07/18/cast-vs-convert-is-there-a-difference-as-far-as-sql-server-is-concerned-which-is-better/
[`COALECSE`]:https://docs.microsoft.com/sql/t-sql/language-elements/coalesce-transact-sql
[`ISNULL`]:https://docs.microsoft.com/sql/t-sql/functions/isnull-transact-sql
[16]:https://www.mssqltips.com/sqlservertip/2689/deciding-between-coalesce-and-isnull-in-sql-server/
[17]:https://nocolumnname.blog/2017/10/09/a-subtle-difference-between-coalesce-and-isnull/
[`DATEADD`]:https://docs.microsoft.com/en-us/sql/t-sql/functions/dateadd-transact-sql
[`DATEDIFF`]:https://docs.microsoft.com/en-us/sql/t-sql/functions/datediff-transact-sql
[`SARGable`]:https://www.sqlshack.com/how-to-use-sargable-expressions-in-t-sql-queries-performance-advantages-and-examples/
[18]:https://michaeljswart.com/2017/12/when-measuring-timespans-try-dateadd-instead-of-datediff/
[19]:https://dba.stackexchange.com/q/132437/107045
[`SET`]:https://docs.microsoft.com/en-gb/sql/t-sql/language-elements/set-local-variable-transact-sql
[`SELECT`]:https://docs.microsoft.com/en-gb/sql/t-sql/language-elements/select-local-variable-transact-sql
[20]:https://assets.red-gate.com/community/books/defensive-database-programming.pdf
[21]:https://www.mssqltips.com/sqlservertip/1888/when-to-use-set-vs-select-when-assigning-values-to-variables-in-sql-server/
[22]:http://vyaskn.tripod.com/differences_between_set_and_select.htm
[`STR`]:https://docs.microsoft.com/en-us/sql/t-sql/functions/str-transact-sql
[23]:https://www.sqlservercentral.com/articles/hidden-formatting-troubles-with-str-sql-spackle
[`ISNUMERIC`]:https://docs.microsoft.com/en-us/sql/t-sql/functions/isnumeric-transact-sql
[`TRY_CONVERT`]:https://docs.microsoft.com/en-us/sql/t-sql/functions/try-convert-transact-sql
[24]:https://www.red-gate.com/hub/product-learning/sql-prompt/sql-prompt-code-analysis-avoid-using-isnumeric-function-e1029
**[⬆ back to top](#table-of-contents)**
<a id="t-sql-programming-style"></a>
## T-SQL Programming Style
SQL Server T-SQL Coding Conventions, Best Practices, and Programming Guidelines.
<a id="#general-t-sql-programming-style"></a>
### General programming T-SQL style
- For database objects names in code use only schema plus object name, do not hardcode server and database names in your code:
```tsql
/* good */
CREATE TABLE dbo.MyTable (MyColumn int);
/* bad*/
CREATE TABLE PRODSERVER.PRODDB.dbo.MyTable (MyColumn int);
CREATE TABLE MyTable (MyColumn int);
```
More details [here](https://www.red-gate.com/simple-talk/opinion/editorials/why-you-shouldnt-hardcode-the-current-database-name-in-your-views-functions-and-stored-procedures/),
[here](https://www.sqlserverscience.com/basics/on-default-schemas-and-search-paths/),
[here](https://www.red-gate.com/hub/product-learning/sql-prompt/finding-code-smells-using-sql-prompt-procedures-lack-schema-qualification),
[here](https://sqlstudies.com/2020/06/22/i-created-a-table-and-sql-created-a-schema-and-a-user/),
[here](https://sqlperformance.com/2014/11/t-sql-queries/multiple-plans-identical-query),
[here](https://sqlblog.org/2019/09/12/bad-habits-to-kick-avoiding-the-schema-prefix).
- Delimiters: **spaces** (not tabs).
- Never use asterisk (`*`) in select statements `SELECT *` and `INSERT` statements, use explicit column names.
Main problems are: traffic issues, Memory Grants issues, Index usage issues.
**Only one exception, see it below.**
More details [here](https://www.red-gate.com/hub/product-learning/sql-prompt/finding-code-smells-using-sql-prompt-asterisk-select-list),
[here](https://sqlblog.org/2009/10/10/bad-habits-to-kick-using-select-omitting-the-column-list),
[here](https://dba.stackexchange.com/q/253873/107045),
[here](https://www.erikdarlingdata.com/sql-server/all-the-problems-with-select/).
- Use asterisk (`*`) only in an archiving situation, where rows are being moved to another table that must have the same structure.
```sql
INSERT INTO SalesOrderArchive /* Note no column list */
SELECT *
FROM SalesOrder
WHERE OrderDate < @OneYearAgo;
DELETE FROM SalesOrder
WHERE OrderDate < @OneYearAgo;
```
If a new column is added to `SalesOrder` table in the future, but not to `SalesOrderArchive`, the `INSERT` will fail.
Which sounds bad, but it's actually a really good thing! Because the alternative is much worse.
If all the columns were listed on the `INSERT` and the `SELECT`, then the `INSERT` would succeed, and so would the following `DELETE` (which is effectively `DELETE *`).
Production code that succeeds doesn't get any attention, and it may be a long time before someone notices that the new column is not being archived, but being silently deleted altogether.
More details [here](https://dba.stackexchange.com/a/253917/107045).
- No square brackets `[]` and [reserved words](https://github.com/ktaranov/sqlserver-kit/blob/master/Scripts/Check_Reserved_Words_For_Object_Names.sql) in object names and alias, use only Latin symbols **`[A-z]`** and numeric **`[0-9]`**.
- Prefer [`ANSI`](http://standards.iso.org/ittf/PubliclyAvailableStandards/c053681_ISO_IEC_9075-1_2011.zip) syntax and functions ([`CAST`][10] instead [`CONVERT`][10], [`COALESE`](https://docs.microsoft.com/en-us/sql/t-sql/language-elements/coalesce-transact-sql) instead [`ISNULL`](https://docs.microsoft.com/en-us/sql/t-sql/functions/isnull-transact-sql), etc.).
- All finished expressions should have semicolon `;` at the end.
This is [`ANSI`] standard and Microsoft announced with the SQL Server 2008 release that semicolon statement terminators will become mandatory in a future version so statement terminators other than semicolons (whitespace) are currently deprecated.
This deprecation announcement means that you should always use semicolon terminators in new development.
From [Transact-SQL Syntax Conventions (Transact-SQL)](https://docs.microsoft.com/en-us/sql/t-sql/language-elements/transact-sql-syntax-conventions-transact-sql):
> Although the semicolon isn't required for most statements in this version of SQL Server, it will be required in a future version.
More details [here](http://www.dbdelta.com/always-use-semicolon-statement-terminators/), [here](https://www.brentozar.com/archive/2015/12/give-your-t-sql-a-semicolonoscopy/), and [here](https://sqlblog.org/2009/09/03/ladies-and-gentlemen-start-your-semi-colons).
- All script files should end with `GO` and line break. This is neccesary for batching scripts run throw `sqlcmd` or another tools.
- Keywords should be in **UPPERCASE**: `SELECT`, `FROM`, `GROUP BY` etc. This increases the readability of the code.
- Data types declaration should be in **lowercase**: `varchar(30)`, `int`, `real`, `nvarchar(max)` etc.
More details [here](https://www.sentryone.com/blog/aaronbertrand/backtobasics-lower-case-data-types).
- All system database and tables must be in **lowercase** for properly working for Case Sensitive instance: `master, sys.tables …`.
- Do not use [nested transactions](https://docs.microsoft.com/en-us/sql/ado/guide/data/transaction-processing#nested-transactions).
The commit of a nested transaction has absolutely no effect – as the only transaction that really exists as far as SQL Server is concerned is the outer one.
More details [here](https://www.sqlskills.com/blogs/paul/a-sql-server-dba-myth-a-day-2630-nested-transactions-are-real/).
- Whenever you have data modification on non-temporary tables, is to use [explicit transactions] over [autocommit].
1. If you have a stored procedure which is simply running a `SELECT` statement, use [autocommit].
2. If you have a stored procedure which performs data modification on non-temporary tables, use an [explicit transactions] only over the area which modifies data.
3. If you are working with non-global temporary tables beforehand, don’t include any modification of those inside the explicit transaction.
4. In a [loop](https://docs.microsoft.com/en-us/sql/t-sql/language-elements/while-transact-sql), choose whether you want to put the [explicit transactions] around the loop or inside it. In most cases, prefer to put the transaction inside the loop to minimize the amount of time that blocking other users.
5. Outside of a stored procedure use [explicit transactions] if you’re doing something potentially risky.
6. Watch out for nested transactions. In SQL Server, there’s very little utility in them and their behavior is weird. [Paul Randal explains in great detail just how broken they are](https://www.sqlskills.com/blogs/paul/a-sql-server-dba-myth-a-day-2630-nested-transactions-are-real/).
More details [here](https://36chambers.wordpress.com/2020/08/10/transaction-modes-in-sql-server/).
- Avoid using [Cross-Database Queries](https://docs.microsoft.com/en-us/sql/relational-databases/in-memory-oltp/cross-database-queries) because it increase backup/restore complexity (you restore one database, then realise you don’t have log backups to bring the other database to the same point in time).
Also Azure SQL Database does not support cross-database queries and you can not migrate into in future.
- Use `temp` tables to reduce network trafic, decrease query complexity and also to get better estimates for modification queries. More details [here](https://www.brentozar.com/archive/2020/04/how-to-get-better-estimates-for-modification-queries/).
`INFORMATION_SCHEMA` views only represent a subset of the metadata of an object. The only reliable way to find the schema of a object is to query the `sys.objects` catalog view.
- When more than one logical operator is used always use parentheses, even when they are not required.
This can improve the readability of queries, and reduce the chance of making a subtle mistake because of operator precedence.
There is no significant performance penalty in using parentheses. More details [here](https://docs.microsoft.com/en-us/sql/relational-databases/query-processing-architecture-guide?view=sql-server-ver15#logical-operator-precedence).
```sql
SELECT
ProductID
FROM Production.Product
WHERE (ProductModelID = 20 OR ProductModelID = 21)
AND Color = 'Red';
```
- Always use aliases for table names. More details [here](https://sqlinthewild.co.za/index.php/2019/04/23/no-this-is-not-a-bug-in-t-sql/).
- <a id="tsql-alias"> Avoid non-standard column and table aliases, use, if required, double-quotes for special characters and always `AS` keyword before alias:
```sql
SELECT
p.LastName AS "Last Name"
FROM dbo.Person AS p;
```
More details [here](https://www.red-gate.com/hub/product-learning/sql-prompt/sql-prompt-code-analysis-avoid-non-standard-column-aliases).
All possible ways using aliases in SQL Server:
```tsql
/* Recommended due to ANSI */
SELECT SCHEMA_NAME(schema_id) + '.' + "name" AS "Tables" FROM sys.tables;
/* Not recommended but possible */
SELECT SCHEMA_NAME(schema_id) + '.' + [name] AS "Tables" FROM sys.tables;
SELECT Tables = SCHEMA_NAME(schema_id) + '.' + [name] FROM sys.tables;
SELECT "Tables" = SCHEMA_NAME(schema_id) + '.' + [name] FROM sys.tables;
SELECT [Tables] = SCHEMA_NAME(schema_id) + '.' + [name] FROM sys.tables;
SELECT 'Tables' = SCHEMA_NAME(schema_id) + '.' + [name] FROM sys.tables;
SELECT SCHEMA_NAME(schema_id) + '.' + [name] [Tables] FROM sys.tables;
SELECT SCHEMA_NAME(schema_id) + '.' + [name] 'Tables' FROM sys.tables;
SELECT SCHEMA_NAME(schema_id) + '.' + [name] "Tables" FROM sys.tables;
SELECT SCHEMA_NAME(schema_id) + '.' + [name] Tables FROM sys.tables;
SELECT SCHEMA_NAME(schema_id) + '.' + [name] AS [Tables] FROM sys.tables;
SELECT SCHEMA_NAME(schema_id) + '.' + [name] AS 'Tables' FROM sys.tables;
SELECT SCHEMA_NAME(schema_id) + '.' + [name] AS Tables FROM sys.tables;
```
- The first argument in `SELECT` expression should be on the next line:
```sql
SELECT
FirstName
```
- Arguments are divided by line breaks, commas should be placed before an argument:
```sql
SELECT
FirstName
, LastName
```
- For SQL Server >= 2012 use [`FETCH-OFFSET`] instead [`TOP`].
More details [here](https://docs.microsoft.com/en-us/sql/t-sql/queries/select-order-by-clause-transact-sql#using-offset-and-fetch-to-limit-the-rows-returned).
But if you use [`TOP`] avoid use [`TOP`] in a `SELECT` statement without an `ORDER BY`.
More details [here](https://www.red-gate.com/hub/product-learning/sql-prompt/finding-code-smells-using-sql-prompt-top-without-order-select-statement).
- If you using [`TOP`] (instead recommended [`FETCH-OFFSET`]) function with round brackets because [`TOP`] has supports use of an expression, such as `(@Rows*2)`, or a sub query: `SELECT TOP(100) LastName …`.
More details [here](https://www.red-gate.com/hub/product-learning/sql-prompt/sql-prompt-code-analysis-avoiding-old-style-top-clause).
Also [`TOP`] without brackets does not work with `UPDATE` and `DELETE` statements.
```tsql
/* Not working without brackets () */
DECLARE @n int = 1;
SELECT TOP@n name FROM sys.objects;
```
- For demo queries use `TOP(100)` or lower value because SQL Server uses one sorting method for `TOP` 1-100 rows, and a different one for 101+ rows.
More details [here](https://www.brentozar.com/archive/2017/09/much-can-one-row-change-query-plan-part-2/).
- Avoid specifying integers in the `ORDER BY` clause as positional representations of the columns in the select list.
The statement with integers is not as easily understood by others compared with specifying the actual column name.
In addition, changes to the select list, such as changing the column order or adding new columns, requires modifying the `ORDER BY` clause in order to avoid unexpected results.
More details [here](https://docs.microsoft.com/en-us/sql/t-sql/queries/select-order-by-clause-transact-sql#best-practices).
```sql
/* bad */
SELECT ProductID, Name FROM production.Production ORDER BY 2;
/* good */
SELECT ProductID, Name FROM production.Production ORDER BY Name;
```
- Avoid wrapping functions around columns specified in the `WHERE` and `JOIN` clauses.
Doing so makes the columns non-deterministic and prevents the query processor from using indexes.
- Use `NULL` or `NOT NULL` for each column in a temporary table. The [`ANSI_NULL_DFLT_ON`] option control the way the Database Engine assigns the `NULL` or `NOT NULL` attributes to columns when these attributes are not specified in a `CREATE TABLE` or `ALTER TABLE` statement.
If a connection executes a procedure with different settings for these options than the connection that created the procedure, the columns of the table created for the second connection can have different nullability and exhibit different behavior. If `NULL` or `NOT NULL` is explicitly stated for each column, the temporary tables are created by using the same nullability for all connections that execute the procedure.
[`ANSI_NULL_DFLT_ON`]:https://docs.microsoft.com/en-us/sql/t-sql/statements/set-ansi-null-dflt-on-transact-sql
- Use modification statements that convert nulls and include logic that eliminates rows with null values from queries. Be aware that in Transact-SQL, `NULL` is not an empty or "nothing" value. It is a placeholder for an unknown value and can cause unexpected behavior, especially when querying for result sets or using AGGREGATE functions.
- Use the `UNION ALL` operator instead of the `UNION` or `OR` operators, unless there is a specific need for distinct values.
The `UNION ALL` operator requires less processing overhead because duplicates are not filtered out of the result set.
- Avoid using `INSERT INTO` a permanent table with `ORDER BY`.
More details [here](https://www.red-gate.com/hub/product-learning/sql-prompt/sql-prompt-code-analysis-insert-permanent-table-order-pe020).
- Avoid using shorthand (`wk, yyyy, d` etc.) with date/time operations, use full names: `month, day, year`.
More details [here](https://sqlblog.org/2011/09/20/bad-habits-to-kick-using-shorthand-with-date-time-operations).
- Avoid ambiguous formats for date-only literals, use `CAST('yyyymmdd' AS DATE)` format.
- Avoid treating dates like strings and avoid calculations on the left-hand side of the `WHERE` clause.
More details [here](https://sqlblog.org/2009/10/16/bad-habits-to-kick-mis-handling-date-range-queries).
- Avoid using [hints](https://docs.microsoft.com/en-us/sql/t-sql/queries/hints-transact-sql) except `RECOMPILE` if needed and `NOEXPAND` (see next tip).
More details [here](https://www.red-gate.com/hub/product-learning/sql-prompt/sql-prompt-code-analysis-a-hint-is-used-pe004-7).
- Use [`NOEXPAND`](https://docs.microsoft.com/en-us/sql/t-sql/queries/hints-transact-sql-table#using-noexpand) hint for [indexed views](https://docs.microsoft.com/sql/relational-databases/views/create-indexed-views) on non enterprise editions and Prior to SQL Server 2016 (13.x) SP1 to let the query optimizer know that we have indexes.
More details [here](https://bornsql.ca/blog/using-indexed-views-dont-forget-this-important-tip/).
- Use [`LOOP JOIN`](https://docs.microsoft.com/en-us/sql/t-sql/queries/hints-transact-sql-query#arguments) and [`FAST 1`](https://docs.microsoft.com/en-us/sql/t-sql/queries/hints-transact-sql-query#arguments) query hints for deleting huge number of rows with `ON DELETE CASCADE` foreign keys specification.
More details [here](https://dba.stackexchange.com/a/262116).
- If you use [hints] always use it with `WITH` keyword because omitting the `WITH` keyword is a deprecated feature and will be removed from future Microsoft SQL Server versions.
One benefit of using the `WITH` keyword is that you can specify multiple table hints using the WITH keyword against the same table.
More details [here](https://www.sqlshack.com/understanding-impact-clr-strict-security-configuration-setting-sql-server-2017/).
- Avoid use of `SELECT…INTO` for production code, use instead `CREATE TABLE` + `INSERT INTO …` approach. More details [here](https://www.red-gate.com/hub/product-learning/sql-prompt/use-selectinto-statement).
- Use only ISO standard JOINS syntaxes. The *old style* Microsoft/Sybase `JOIN` style for SQL, which uses the `=*` and `*=` syntax, has been deprecated and is no longer used.
Queries that use this syntax will fail when the database engine level is 10 (SQL Server 2008) or later (compatibility level 100). The ANSI-89 table citation list (`FROM tableA, tableB`) is still ISO standard for `INNER JOINs` only. Neither of these styles are worth using.
It is always better to specify the type of join you require` INNER`, `LEFT OUTER`, `RIGHT OUTER`, `FULL OUTER` and `CROSS`, which has been standard since ANSI SQL-92 was published. While you can choose any supported `JOIN `style, without affecting the query plan used by SQL Server, using the ANSI-standard syntax will make your code easier to understand, more consistent, and portable to other relational database systems.
More details [here](https://www.red-gate.com/hub/product-learning/sql-prompt/finding-code-smells-using-sql-prompt-old-style-join-syntax-st001).
- Do not use a scalar user-defined function (UDF) in a `JOIN` condition, `WHERE` search condition, or in a `SELECT` list, unless the function is [schema-bound](https://docs.microsoft.com/en-us/sql/t-sql/statements/create-function-transact-sql#best-practices).
More details [here](https://www.red-gate.com/hub/product-learning/sql-prompt/misuse-scalar-user-defined-function-constant-pe017).
- For scalar function use [`WITH SCHEMABINDING`](https://docs.microsoft.com/en-us/sql/t-sql/statements/create-function-transact-sql#best-practices) option to get a performance boost. More details [here](https://bertwagner.com/2018/12/04/two-words-for-faster-scalar-functions/)
- Do not use [`INFORMATION_SCHEMA`] views to determine the schema of an object. [`INFORMATION_SCHEMA`] views only represent a **subset of the metadata** of an object.
The only reliable way to find the schema of a object is to query the [`sys.objects`](https://docs.microsoft.com/en-us/sql/relational-databases/system-catalog-views/sys-objects-transact-sql) catalog view.
More details [here](https://github.com/MicrosoftDocs/sql-docs/issues/4188).
- Do not use explicit transactions for DML and DDL especially for reorganize index because the locking behavior of this statemnets becomes more restrictive.
More details [here](https://github.com/MicrosoftDocs/sql-docs/pull/4011).
- In [sqlcmd](https://docs.microsoft.com/en-us/sql/tools/sqlcmd-utility) move the `-U`and `-P` parameters after the `-Q` parameter so that the password is at the end of the command.
More details [here](https://bornsql.ca/blog/the-curious-case-of-the-sqlcmd-password/)
```
sqlcmd -S MSSQLSERVER$EXPRESS -Q "dbcc checkdb ('master') with DATA_PURITY, NO_INFOMSGS;" -U maintenanceUser -P ""weirdPassword
```
- Use `EXISTS` or `NOT EXISTS` if referencing a subquery, and `IN` or `NOT IN` when have a list of literal values.
More details [here](https://www.brentozar.com/archive/2018/08/a-common-query-error/).
- For concatenate unicode strings:
- always using the upper-case `N`;
- always store into a variable of type `nvarchar(max)`;
- avoid truncation of string literals, simply ensure that one piece is converted to `nvarchar(max)`.
Example:
```tsql
/* good */
DECLARE @nvcmaxVariable nvarchar(max);
SET @nvcmaxVariable = CAST(N'ಠ russian anomaly ЯЁЪ ಠ ' AS nvarchar(max)) + N'something else' + N'another';
SELECT @nvcmaxVariable;
```
More details [here](https://themondaymorningdba.wordpress.com/2018/09/13/them-concatenatin-blues/).
- Always specify a length to any text-based data type such as `varchar`, `nvarchar`, `char`, `nchar`:
```tsql
/* bad */
DECLARE @myBadVarcharVariable varchar;
DECLARE @myBadNVarcharVariable nvarchar;
DECLARE @myBadCharVariable char;
DECLARE @myBadNCharVariable nchar;
/* good */
DECLARE @myGoodVarchareVariable varchar(50);
DECLARE @myGoodNVarchareVariable nvarchar(90);
DECLARE @myGoodCharVariable char(7);
DECLARE @myGoodNCharVariable nchar(10);
```
More details [here](https://www.red-gate.com/hub/product-learning/sql-prompt/using-a-variable-length-datatype-without-explicit-length-the-whys-and-wherefores) and [here](https://sqlblog.org/2009/10/09/bad-habits-to-kick-declaring-varchar-without-length).
- Use only [`ORIGINAL_LOGIN()`](https://docs.microsoft.com/en-us/sql/t-sql/functions/original-login-transact-sql) function because is the only function that consistently returns the actual login name that we started with regardless of impersonation.
More details [here](https://sqlstudies.com/2015/06/24/which-user-function-do-i-use/).
- Always use `IF` statement with `BEGIN-END` block to prevent errors with multi line statements:
```tsql
DECLARE @x int = 0;
DECLARE @y int = 1;
/* bad */
IF @y > @x
SET @x = @x + 1;
SET @y = @y - 1;
ELSE
PRINT(1);
/* Msg 156, Level 15, State 1, Line 8
Incorrect syntax near the keyword 'ELSE'. */
/* good */
IF @y > @x
BEGIN
SET @x = @x + 1;
SET @y = @y - 1;
END;
ELSE
BEGIN
PRINT(1);
END;
```
- `FROM, WHERE, INTO, JOIN, GROUP BY, ORDER BY` expressions should be aligned so, that all their arguments are placed under each other (see Example below)
TSQL Example with formating:
```tsql
WITH CTE_MyCTE AS (
SELECT
t1.Value1 AS Val1
, t1.Value2 AS Val2
, t2.Value3 AS Val3
INNER JOIN dbo.Table3 AS t2
ON t1.Value1 = t2.Value1
WHERE t1.Value1 > 1
AND t2.Value2 >= 101
)
SELECT
t1.Value1 AS Val1
, t1.Value2 AS Val2
, t2.Value3 AS Val3
INTO #Table3
FROM CTE_MyCTE AS t1
ORDER BY t2.Value2;
```
**[⬆ back to top](#table-of-contents)**
<a id="programming-style"></a>
### Stored procedures and functions programming style
Recommendations from Microsoft: [Stored procedure Best practice][11]
- All stored procedures and functions should use `ALTER` statement and start with the object presence check (see example below) for saving `GRANTs` on your object.
Also if you use Query Store and plan forcing and `DROP` and then `CREATE` new object you loosing plan forcing, more details [here](https://www.scarydba.com/2020/03/02/query-store-plan-forcing-and-drop-create/).
For SQL Server 2016 and higher you can use new `CREATE OR ALTER` statement.
- `ALTER` statement should be preceded by 2 line breaks
- Parameters name should be in **camelCase**
- Parameters should be placed under procedure name divided by line breaks
- After the `ALTER` statement and before `AS` keyword should be placed a comment with execution example
- The procedure or function should begin with parameters checks (see example below)
- Create `sp_` procedures only in `master` database - SQL Server will always scan through the system catalog first
- Always use `BEGIN TRY` and `BEGIN CATCH` for error handling
- Always use multi-line comment `/* */` instead in-line comment `--`
- Use `SET NOCOUNT ON;` for stops the message that shows the count of the number of rows affected by a Transact-SQL statement and decreasing network traffic.
More details [here](https://www.red-gate.com/hub/product-learning/sql-prompt/finding-code-smells-using-sql-prompt-set-nocount-problem-pe008-pe009) and [here][11].
- Do not use `SET NOCOUNT OFF;` because it is default behavior
- Use `RAISERROR` instead `PRINT` if you want to give feedback about the state of the currently executing SQL batch without lags.
More details [here](http://sqlity.net/en/984/print-vs-raiserror/) and [here](http://sqlservercode.blogspot.com/2019/01/print-disruptor-of-batch-deletes-in-sql.html).
- Call natively-compiled stored procedures without named parameters.
More details [here](https://sqlperformance.com/2015/06/t-sql-queries/how-not-to-call-hekaton-procedures).
- All code should be self documenting
- T-SQL code, triggers, stored procedures, functions, scripts, should have a standard comment-documentation banner:
```
<documentation>
<summary>Get all databases meta data using dynamic T-SQL</summary>
<returns>1 data set: temp table #DatabaseInfo.</returns>
<issues>No</issues>
<author>Konstantin Taranov</author>
<created>2018-03-01</created>
<modified>2019-11-14 by Konstantin Taranov</modified>
<version>1.2</version>
<sourceLink>https://github.com/ktaranov/sqlserver-kit/blob/master/Scripts/Databases_Report.sql</sourceLink>
</documentation>
```
**[⬆ back to top](#table-of-contents)**
Stored Procedure Example:
```tsql
IF OBJECT_ID('dbo.usp_StoredProcedure', 'P') IS NULL
EXECUTE('CREATE PROCEDURE dbo.usp_StoredProcedure as SELECT 1');
GO
ALTER PROCEDURE dbo.usp_StoredProcedure(
@parameterValue1 smallint
, @parameterValue2 nvarchar(300)
, @debug bit = 0
)
/*
<documentation>
<summary>Simple example of tsql procedure</summary>
<returns>nothing</returns>
<issues>No</issues>
<author>Konstantin Taranov</author>
<created>2019-01-01</created>
<modified>2019-11-25 by Konstantin Taranov</modified>
<version>1.2</version>
<sourceLink>-</sourceLink>
<example1>EXECUTE dbo.usp_StoredProcedure
@parameterValue1 = 0
, @parameterValue2 = N'BULK'</example1>
</documentation>
*/
AS
SET NOCOUNT ON;
BEGIN TRY
IF (@parameterValue1 < 0 OR @parameterValue2 NOT IN ('SIMPLE', 'BULK', 'FULL'))
RAISERROR('Not valid data parameter!', 16, 1);
IF (@debug) PRINT @parameterValue2;
END TRY
BEGIN CATCH
/* Print error information. */
PRINT 'Error: ' + CAST(ERROR_NUMBER()) AS varchar(50)) +
', Severity: ' + CAST(ERROR_SEVERITY(), varchar(5)) +
', State: ' + CAST(ERROR_STATE(), varchar(5) ) +
', Procedure: ' + COALESCE(ERROR_PROCEDURE(), '-') +
', Line: ' + CAST(ERROR_LINE(), varchar(5)) +
', User name: ' + CAST(ORIGINAL_LOGIN(), sysname);
PRINT ERROR_MESSAGE();
END CATCH;
GO
```
**[⬆ back to top](#table-of-contents)**
<a id="dynamic-t-sql-recommendation"></a>
### Dynamic T-SQL Recommendation
**Highly recommended to read awesome detailed article about dynamic T-SQL by Erland Sommarskog: [The Curse and Blessings of Dynamic SQL](http://sommarskog.se/dynamic_sql.html)**
Dynamic SQL is a programming technique that allows you to construct SQL statements dynamically at runtime.
It allows you to create more general purpose and flexible SQL statement because the full text of the SQL statements may be unknown at compilation.
For example, you can use the dynamic SQL to create a stored procedure that queries data against a table whose name is not known until runtime.
More details [here](http://www.sqlservertutorial.net/sql-server-stored-procedures/sql-server-dynamic-sql/).
- Do not use [nvarchar(max)][6] for your object’s name parameter, use [sysname](https://docs.microsoft.com/en-us/previous-versions/sql/sql-server-2008-r2/ms191240(v=sql.105)?redirectedfrom=MSDN) instead (synonym for nvarchar(128) except that, by default, sysname is NOT NULL).
```tsql
/* Bad */
DECLARE @tableName nvarchar(max) = N'MyTableName';
/* Good */
DECLARE @tableName sysname = N'MyTableName';
```
- Do quote the names of your objects properly.
```tsql
/* Bad */
DECLARE @tsql nvarchar(max);
DECLARE @tableName sysname = N'My badly named table!';
SET @tsql = N'SELECT object_id FROM ' + @tableName;
/* Good */
DECLARE @tsql nvarchar(max);
DECLARE @tableName sysname = N'My badly named table 111!';
SET @tsql = N'SELECT object_id FROM ' + QUOTENAME(@tableName);
```
- Always use [`sp_executesql`] instead [`EXEC`] to prevent sql injection.
Also [`sp_executesql`] can parameterizing your dynamic statement that means plans can be reused as well (when the value of the dynamic object is the same).
Also [`sp_executesql`] can even be used to output values as well (see example below).
```tsql
/* Bad EXEC example with sql injection*/
DECLARE @tsql nvarchar(max);
DECLARE @tableName sysname = N'master.sys.tables; SELECT * FROM master.sys.server_principals;';
SET @tsql = N'SELECT "name" FROM ' + @tableName + N';';
EXEC (@tsql);
/* Good sp_executesql example*/
DECLARE @tsql nvarchar(max);
DECLARE @tableName sysname = N'master.sys.tables';
DECLARE @id int = 2107154552;
SET @tsql = N'SELECT name FROM ' + @tableName +
N' WHERE object_id = ' + CONVERT(nvarchar(max), @id);
EXEC sp_executesql @tsql, N'@ID int', @ID = @id;
/* Good sp_executesql example with OUTPUT */
DECLARE @tsql nvarchar(max);
DECLARE @tableName sysname = N'master.sys.tables';
DECLARE @count bigint;
SET @tsql = N'SELECT @countOUT = COUNT(*) FROM ' + @tableName + N';';
EXEC sp_executesql @tsql, N'@countOUT bigint OUTPUT', @countOUT = @count OUTPUT;
PRINT('@count = ' + CASE WHEN @count IS NULL THEN 'NULL' ELSE CAST(@count AS varchar(30)) END);
```
- Do not use dynamic T-SQL if your statement is not dynamic.
```tsql
/* Bad */
DECLARE @tsql nvarchar(max);
DECLARE @id int = 2107154552;
SET @tsql = N'SELECT object_id, "name" FROM master.sys.tables WHERE object_id = ' + CAST(@id AS nvarchar(max));
EXEC sp_executesql @tsql;
/* Good */
DECLARE @id int = 2107154552;
SELECT object_id, "name" FROM master.sys.tables WHERE object_id = @id;
```
- Do not debug the code that creates the dynamic T-SQL first, debug the generated T-SQL statement instead.
Use `@debug` variable to print (or a `SELECT` statement if your dynamic T-SQL is over 4000 characters) dynamic statement instead executing it.
See example below.
- Do take the time to format your dynamic T-SQL.
```tsql
/* Bad @tsql formating */
DECLARE @tsql nvarchar(max);
DECLARE @sep nvarchar(30) = ' UNION ALL ';
DECLARE @debug bit = 1;
SELECT @tsql = COALESCE(@tsql, N'') +
N'SELECT N' + QUOTENAME(name,'''') +
N' AS DBName, (SELECT COUNT(*) FROM ' +
QUOTENAME(name) + N'.sys.tables) AS TableCount' +
@sep
FROM sys.databases
ORDER BY name;
SET @tsql = LEFT(@tsql, LEN(@tsql) - LEN(@sep));
IF @debug = 1 SELECT @tsql AS "tsql" ELSE EXEC sp_executesql @tsql;
/* Good @tsql formating */
DECLARE @tsql nvarchar(max);
DECLARE @sep nvarchar(30) = ' UNION ALL ';
DECLARE @debug bit = 1;
DECLARE @crlf nvarchar(10) = NCHAR(13) + NCHAR(10);
SELECT @tsql = COALESCE(@tsql, N'') + @crlf +
N'SELECT N' + QUOTENAME(name,'''') + N' AS DBName' + @crlf +
N' , (SELECT COUNT(*) FROM ' + QUOTENAME(name) + N'.sys.tables) AS TableCount' + @crlf +
@sep
FROM sys.databases
ORDER BY name;
SET @tsql = LEFT(@tsql, LEN(@tsql) - LEN(@sep)) + N';';
IF @debug = 1 SELECT @tsql AS "tsql" ELSE EXEC sp_executesql @tsql;
```
**[⬆ back to top](#table-of-contents)**
<a id="reference"></a>
## Official Reference and useful links
- [Transact-SQL Formatting Standards](https://www.simple-talk.com/sql/t-sql-programming/transact-sql-formatting-standards-%28coding-styles%29/) (by Robert Sheldon)
- [Subjectivity: Naming Standards](http://blogs.sqlsentry.com/aaronbertrand/subjectivity-naming-standards/) (by Aaron Bertrand)
- [General Database Conventions](http://kejser.org/database-naming-conventions/general-database-conventions/) (by Thomas Kejser)
- [Writing Readable SQL](http://www.codeproject.com/Articles/126380/Writing-Readable-SQL) (by Red Gate)
- [SQL Style Guide](http://www.sqlstyle.guide/) (by Simon Holywell)
- [SQL Code Layout and Beautification](https://www.simple-talk.com/sql/t-sql-programming/sql-code-layout-and-beautification/) (by William Brewer)
- [TSQL Coding Style](http://www.databasejournal.com/features/mssql/tsql-coding-style.html) (by Gregory Larsen)
- [User-Defined Functions](https://docs.microsoft.com/en-us/sql/relational-databases/user-defined-functions/user-defined-functions)
- [Synonyms (Database Engine)](https://docs.microsoft.com/en-us/sql/relational-databases/synonyms/synonyms-database-engine)
- [Primary and Foreign Key Constraints](https://docs.microsoft.com/en-us/sql/relational-databases/tables/primary-and-foreign-key-constraints)
- [sys.objects](https://docs.microsoft.com/en-us/sql/relational-databases/system-catalog-views/sys-objects-transact-sql)
- [SQL Server Constraints](https://docs.microsoft.com/en-us/sql/t-sql/statements/alter-table-table-constraint-transact-sql)
- [CHECK Constraint TECHNET](http://technet.microsoft.com/en-us/library/ms188258%28v=sql.105%29.aspx)
- [SQL Server CLR Integration](https://docs.microsoft.com/en-us/dotnet/framework/data/adonet/sql/introduction-to-sql-server-clr-integration)
- [Deploying CLR Database Objects](https://docs.microsoft.com/en-us/sql/relational-databases/clr-integration/deploying-clr-database-objects)
- [CLR Stored Procedures](https://docs.microsoft.com/en-us/sql/database-engine/dev-guide/clr-stored-procedures)
- [User-defined Functions](https://docs.microsoft.com/en-us/sql/relational-databases/user-defined-functions/create-user-defined-functions-database-engine)
- [SET NOCOUNT ON (Transact-SQL)](https://docs.microsoft.com/en-us/sql/t-sql/statements/set-nocount-transact-sql)
- [T-SQL Coding Guidelines Presentation](http://www.slideshare.net/chris1adkin/t-sql-coding-guidelines) (by Chris Adkin)
- [Sql Coding Style](http://c2.com/cgi/wiki?SqlCodingStyle)
- [SQL Server Code Review Checklist for Developers](https://www.sqlshack.com/sql-server-code-review-checklist-for-developers/) (by Samir Behara)
- [SQL Formatting standards – Capitalization, Indentation, Comments, Parenthesis](https://solutioncenter.apexsql.com/sql-formatting-standards-capitalization-indentation-comments-parenthesis/) (by ApexSQL)
- [In The Cloud: The Importance of Being Organized](http://sqlblog.com/blogs/john_paul_cook/archive/2017/05/16/in-the-cloud-the-importance-of-being-organized.aspx)
- [Naming Conventions in Azure](http://www.sqlchick.com/entries/2017/6/24/naming-conventions-in-azure)
- [The Basics of Good T-SQL Coding Style – Part 3: Querying and Manipulating Data](https://www.simple-talk.com/sql/t-sql-programming/basics-good-t-sql-coding-style-part-3-querying-manipulating-data/)
- [SQL naming conventions](https://www.red-gate.com/simple-talk/blogs/sql-naming-conventions/) (by Phi Factor)
- [SQL Server Compact Object Limitations](http://technet.microsoft.com/en-us/library/ms172451%28v=sql.110%29.aspx)
- [Dos and Don'ts of Dynamic SQL](https://www.sqlservercentral.com/articles/dos-and-donts-of-dynamic-sql) (by Thom Andrews)
**[⬆ back to top](#table-of-contents)**
[`TOP`]:https://docs.microsoft.com/it-it/sql/t-sql/queries/top-transact-sql
[`FETCH-OFFSET`]:https://docs.microsoft.com/en-us/sql/t-sql/queries/select-order-by-clause-transact-sql
[`sp_executesql`]:https://docs.microsoft.com/en-us/sql/relational-databases/system-stored-procedures/sp-executesql-transact-sql
[`EXEC`]:https://docs.microsoft.com/en-us/sql/t-sql/language-elements/execute-transact-sql
[10]:https://docs.microsoft.com/en-us/sql/t-sql/functions/cast-and-convert-transact-sql
[`INFORMATION_SCHEMA`]:https://docs.microsoft.com/en-us/sql/relational-databases/system-information-schema-views/system-information-schema-views-transact-sql
[11]:https://docs.microsoft.com/en-us/sql/t-sql/statements/create-procedure-transact-sql#best-practices
[explicit transactions]:https://docs.microsoft.com/en-us/sql/t-sql/language-elements/transactions-transact-sql
[autocommit]:https://docs.microsoft.com/en-us/sql/t-sql/statements/set-implicit-transactions-transact-sql
[`ANSI`]:http://standards.iso.org/ittf/PubliclyAvailableStandards/c053681_ISO_IEC_9075-1_2011.zip
[hints]https://docs.microsoft.com/en-us/sql/t-sql/queries/hints-transact-sql
Reference in New Issue View Git Blame Copy Permalink