naming-convention/SQL Server Name Convention and T-SQL Programming Style.md

SQL Server Name Convention and T-SQL Programming Style

Table of Contents

• SQL Server Object Name Convention
• T-SQL Programming Style
  • General programming style
  • Stored procedures and functions programming style
• Official Reference and useful links

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 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

• 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. All possible ways using aliases in SQL Server:

   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:

  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. 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

• 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. For stored procedure more details here

• All system database and tables must be in lower case for properly working in Case Sensitive instance: master, sys.tables…

• Avoid using ISNUMERIC function. Use for SQL Server >= 2012 TRY_CONVERT function and for SQL Server < 2012 LIKE expression:

  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

• Avoid using INSERT INTO a permanent table with ORDER BY, more details here

• Avoid using shorthand (wk, yyyy, d etc.) with date/time operations, use full names: month, day, year. More details here

• https://sqlblog.org/2009/10/16/bad-habits-to-kick-mis-handling-date-range-queries

Example:

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. More details here
• Do not use SET NOCOUNT OFF; (because it is default behavior)
• Use TOP expression with ():

-- 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:

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:

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;

GO

⬆ back to top

Official Reference and useful links

• Transact-SQL Formatting Standards (by Robert Sheldon)
• Subjectivity: Naming Standards (by Aaron Bertrand)
• General Database Conventions (by Thomas Kejser)
• Writing Readable SQL (by Red Gate_)
• SQL Style Guide (by Simon Holywell)
• SQL Code Layout and Beautification (by William Brewer)
• TSQL Coding Style (by Gregory Larsen)
• Database object Limitations
• User-Defined Functions MSDN
• Synonim TECHNET
• Primary and Foreign Key Constraints MSDN
• sys.objects MSDN
• Constraints TECHNET
• CHECK Constraint TECHNET
• SQL Server CLR Integration MSDN
• CLR Databse Objects MSDN
• CLR Stored Procedures
• User-defined Functions
• MSDN SET NOCOUNT ON
• T-SQL Coding Guidelines Presentation (by Chris Adkin)
• Sql Coding Style
• SQL Server Code Review Checklist for Developers (by Samir Behara)
• SQL Formatting standards – Capitalization, Indentation, Comments, Parenthesis (by ApexSQL)
• In The Cloud: The Importance of Being Organized
• Naming Conventions in Azure
• The Basics of Good T-SQL Coding Style – Part 3: Querying and Manipulating Data

⬆ back to top