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# SQL Server Name Convention and T-SQL Programming Style
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)
- [Database object Limitations](http://technet.microsoft.com/en-us/library/ms172451%28v=sql.110%29.aspx)
- [User-Defined Functions MSDN](http://msdn.microsoft.com/en-us/library/ms191007.aspx)
- [Synonim TECHNET](http://technet.microsoft.com/en-us/library/ms187552(v=sql.110).aspx)
- [Primary and Foreign Key Constraints MSDN](http://msdn.microsoft.com/en-us/library/ms179610.aspx)
- [sys.objects MSDN](http://msdn.microsoft.com/en-us/library/ms190324.aspx)
- [Constraints TECHNET](http://technet.microsoft.com/en-us/library/ms189862%28v=sql.105%29.aspx)
- [CHECK Constraint TECHNET](http://technet.microsoft.com/en-us/library/ms188258%28v=sql.105%29.aspx)
- [SQL Server CLR Integration MSDN](http://msdn.microsoft.com/en-us/library/ms254498%28v=vs.110%29.aspx)
- [CLR Databse Objects MSDN](http://msdn.microsoft.com/en-us/library/ms345099%28SQL.100%29.aspx)
- [CLR Stored Procedures](http://msdn.microsoft.com/en-us/library/ms131094%28v=sql.100%29.aspx)
- [User-defined Functions](http://msdn.microsoft.com/en-us/library/ms191320.aspx)
- [MSDN SET NOCOUNT ON](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 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 |
| Database Trigger | | PascalCase | 50 | No | DTR_ | No | Yes | [A-z] | DTR_CheckLogin |
| Schema | | lowercase | 30 | No | No | No | Yes | [A-z][0-9] | myschema |
| File Table | | PascalCase | 128 | No | FT_ | No | Yes | [A-z][0-9] | FT_MyTable |
| 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 |
| Table | U | PascalCase | 128 | No | No | No | Yes | [A-z][0-9] | MyTable |
| Table Column | | PascalCase | 128 | No | No | No | Yes | [A-z][0-9] | MyColumn |
| Table Default Values | D | PascalCase | 128 | No | DF_ | No | Yes | [A-z][0-9] | DF_MyTable_MyColumn |
| Table Check Column Constraint | C | PascalCase | 128 | No | CK_ | No | Yes | [A-z][0-9] | CK_MyTable_MyColumn |
| Table Check Table Constraint | C | PascalCase | 128 | No | CTK_ | No | Yes | [A-z][0-9] | CTK_MyTable_MyColumn_AnotherColumn |
| Table Primary Key | PK | PascalCase | 128 | No | PK_ | No | Yes | [A-z][0-9] | PK_MyTableID |
| Table 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 |
| Table Trigger | TR | PascalCase | 128 | No | TR_ | No | Yes | [A-z][0-9] | TR_MyTable_LogicalName |
| View | V | PascalCase | 128 | No | VI_ | No | No | [A-z][0-9] | VI_LogicalName |
| 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 |
## T-SQL Programming Style
SQL Server TSQL Coding Conventions, Best Practices, and Programming Guidelines
### General programming style
- Delimiters: spaces (not tabs)
- No square brackets [] and reserved words in object names and alias, use only Latin symbols **[A-z]** and numeric **[0-9]**
- Prefer [ANSI syntax](http://standards.iso.org/ittf/PubliclyAvailableStandards/c053681_ISO_IEC_9075-1_2011.zip) and functions
- All finished expressions should have `;` 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.)
More details [here](http://www.dbdelta.com/always-use-semicolon-statement-terminators/)
- All script files should end with `GO` and line break
- Avoid non-standard column aliases, use ,if required, double-quotes and always `AS` keyword: `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 of aliases in SQL Server:
```sql
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;
SELECT Schema_Name(schema_id)+'.'+[name] AS Tables FROM sys.tables;
```
- The first argument in `SELECT` expression should be on the same line with it: `SELECT LastName …`
- Arguments are divided by line breaks, commas should be placed before an argument:
```sql
SELECT FirstName
, LastName
```
- Use `TOP` function with brackets because `TOP` has supports use of an expression, such as `(@Rows*2)`, or a subquery: `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.
- For demo queries use TOP(100) or lower value because SQL Server 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/)
- Keywords and data types declaration should be in **UPPERCASE**
- `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)
- All objects must used with schema names but without database and server name: `FROM dbo.Table`
- All system database and tables must be in lower case for properly working in Case Sensitive instance: `master, sys.tables…`
- Avoid using [`ISNUMERIC`](https://docs.microsoft.com/en-us/sql/t-sql/functions/isnumeric-transact-sql) function. Use for SQL Server >= 2012 [`TRY_CONVERT`](https://docs.microsoft.com/en-us/sql/t-sql/functions/try-convert-transact-sql) function and for SQL Server < 2012 `LIKE` expression:
```sql
CASE WHEN Stuff(LTrim(TapAngle),1,1,'') NOT LIKE '%[^-+.ED0123456789]%' --is it a float?
AND Left(LTrim(TapAngle),1) LIKE '[-.+0123456789]'
AND TapAngle LIKE '%[0123456789][ED][-+0123456789]%'
AND Right(TapAngle ,1) LIKE N'[0123456789]'
THEN 'float'
WHEN Stuff(LTrim(TapAngle),1,1,'') NOT LIKE '%[^.0123456789]%' --is it numeric
AND Left(LTrim(TapAngle),1) LIKE '[-.+0123456789]'
AND TapAngle LIKE '%.%' AND TapAngle NOT LIKE '%.%.%'
AND TapAngle LIKE '%[0123456789]%'
THEN 'float'
ELSE NULL
END
```
More details [here](https://www.red-gate.com/hub/product-learning/sql-prompt/sql-prompt-code-analysis-avoid-using-isnumeric-function-e1029)
- 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)
Example:
```sql
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;
```
### Stored procedures and functions programming style
- All stored procedures and functions should use `ALTER` statement and start with the object presence check
- `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 parameter check
- Create `sp_` procedures only in `master` database - SQL Server will always scan through the system catalog first
- Always use `BEGIN TRY` and `BEGIN CATCH`
- Always use `/* */` instead inline comment `--`
- Use `SET NOCOUNT ON;` for stops the message that shows the count of the number of rows affected by a Transact-SQL statement
- Use TOP expression with `()`:
```tsql
-- Not working without ()
DECLARE @n int = 1;
SELECT TOP@n name FROM sys.objects;
```
- All code should be self documenting
- TSQL code, triggers, stored procedures, functions, should have a standard comment banner:
```tsql
summary: >
This procedure returns an object build script as a single-row, single column
result.
Revisions:
- Author: Bill Gates
Version: 1.1
Modification: dealt properly with heaps
date: 2017-07-15
- version: 1.2
modification: Removed several bugs and got column-level constraints working
date: 2017-06-30
example:
- code: udf_MyFunction 'testValsue';
returns: >
single row, single column result Build_Script.
```
Stored Procedure Example:
```sql
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
)
/*
EXECUTE dbo.usp_StoredProcedure
@parameterValue1 = 0
, @parameterValue2 = N'BULK'
*/
AS
SET NOCOUNT ON;
BEGIN TRY
IF (@parameterValue1 < 0 OR @parameterValue2 NOT IN ('SIMPLE', 'BULK', 'FULL'))
RAISERROR('Not valid data parameter!', 16, 1);
PRINT @parameterValue2;
END TRY
BEGIN CATCH
-- Print error information.
PRINT 'Error: ' + CONVERT(varchar(50), ERROR_NUMBER()) +
', Severity: ' + CONVERT(varchar(5), ERROR_SEVERITY()) +
', State: ' + CONVERT(varchar(5), ERROR_STATE()) +
', Procedure: ' + ISNULL(ERROR_PROCEDURE(), '-') +
', Line: ' + CONVERT(varchar(5), ERROR_LINE()) +
', User name: ' + CONVERT(sysname, CURRENT_USER);
PRINT ERROR_MESSAGE();
END CATCH;
SET NOCOUNT OFF;
GO
```
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