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MSSQL Patterns

Table of contents

  1. Columns
  2. Constraints
  3. Indexes
  4. Tables
  5. Views
  6. Triggers
  7. Procedures
  8. Documentation
  9. Users

Reserved words checking tool

https://www.petefreitag.com/tools/sql_reserved_words_checker

Indexes

Drop Index

DROP INDEX IF EXISTS [schema].[table].[index_name];

Create Index

IF EXISTS(SELECT * FROM sys.indexes WHERE object_id = object_id('schema.table') AND NAME ='index_name')
BEGIN
    DROP INDEX index_name ON schema.table;
END
CREATE INDEX index_name ON schema.table([column_list]);

Constraints

Drop a default value

    ALTER TABLE [schema].[table]
    DROP CONSTRAINT IF EXISTS [DF_<name>];

Add a default value

    IF NOT EXISTS (
            select *
              from sys.all_columns c
                   join sys.tables t on t.object_id = c.object_id
                   join sys.schemas s on s.schema_id = t.schema_id
                   join sys.default_constraints d on c.default_object_id = d.object_id
             where t.name = 'table'
               and c.name = 'columnName'
               and s.name = 'schema')
        ALTER TABLE [schema].[table]
        ADD CONSTRAINT [DF_<name>]
        DEFAULT <defaultValue> FOR [columnName];

Drop a Foreign Key constraint

IF EXISTS(SELECT *
            FROM INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE
           WHERE CONSTRAINT_COLUMN_USAGE.TABLE_SCHEMA = 'schema'
             AND CONSTRAINT_COLUMN_USAGE.TABLE_NAME = 'table'
             AND CONSTRAINT_COLUMN_USAGE.COLUMN_NAME = 'columnName'
             AND CONSTRAINT_NAME = 'FK_<name>')
    BEGIN
        ALTER TABLE [schema].[table]
            DROP CONSTRAINT [FK_<name>];
    END

Or simply

ALTER TABLE [schema].[table] DROP CONSTRAINT IF EXISTS [FK_<name>];

Add a Foreign Key Constraint

IF NOT EXISTS(SELECT *
                FROM INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE
               WHERE CONSTRAINT_COLUMN_USAGE.TABLE_SCHEMA = 'schema'
                 AND CONSTRAINT_COLUMN_USAGE.TABLE_NAME = 'table'
                 AND CONSTRAINT_COLUMN_USAGE.COLUMN_NAME = 'columnName'
                 AND CONSTRAINT_NAME = 'FK_<name>')
    BEGIN
        ALTER TABLE [schema].[table]
            ADD CONSTRAINT [FK_<name>]
                FOREIGN KEY (colName) REFERENCES [schema].[table] (columnName);
    END

Columns

Drop a column

IF EXISTS(
        SELECT * FROM sys.columns
         WHERE object_ID=object_id('schema.table')
           AND col_name(object_ID,column_Id)='columnName'
    )
    BEGIN
        ALTER TABLE [schema].[table]
            DROP COLUMN [columnName];
    END;

Or, more simply

 ALTER TABLE [schema].[table] DROP COLUMN IF EXISTS  [columnName1], COLUMN IF EXISTS [columnName2], ...;

Add a column

IF NOT EXISTS(
                SELECT *
                FROM sys.columns
               WHERE object_ID = object_id('schema.table')
                 AND col_name(object_ID, column_Id) = 'columnName')
    BEGIN
        ALTER TABLE [schema].[table]
            ADD [columnName] <type>;               
    END

Add a column with a named default value

ALTER TABLE [schema].[table]
ADD [columnName] <type>
CONSTRAINT [DF_<columnName>] DEFAULT 'defaultValue' NOT NULL;

Remove NOT NULL

ALTER TABLE
  tblname
ALTER COLUMN
  colname
    NVARCHAR(20) NOT NULL;

Tables

Drop table (SQL Server 2019)

DROP TABLE IF EXISTS [schema].[table];

Create a table

IF NOT EXISTS(SELECT *
                FROM INFORMATION_SCHEMA.TABLES
               WHERE TABLE_NAME = 'tableName'
                 AND TABLE_SCHEMA = 'schema')
BEGIN
    <table definition>
END

Views

Drop a view

DROP VIEW IF EXISTS [schema].[viewName];

Create a view

CREATE OR ALTER VIEW [schema].[viewName]
AS
SELECT * from [schema.table];

Triggers

You can find out if a trigger exists using something like:

SELECT * FROM sys.triggers
WHERE [parent_id] = OBJECT_ID('schema.table')
AND [name] = 'triggerName';

Note: SQL Server 2019 - dropping a table automatically drops any associated triggers.

Drop a Trigger

DROP TRIGGER IF EXISTS [schema].[triggerName];

Create a trigger

You probably want to make sure the table for the trigger exists and then ensure that the latest trigger definition is applied. We have to use EXEC to run the CREATE TRIGGER command as otherwise we will get a syntax error. It must be the first statement in the batch. Using CREATE OR ALTER TRIGGER means any old definition will be updated with the latest.

IF EXISTS(SELECT *
            FROM INFORMATION_SCHEMA.TABLES
           WHERE TABLE_NAME = 'tableName'
             AND TABLE_SCHEMA = 'schema')
EXEC('CREATE OR ALTER TRIGGER [schema].[triggerName]
    ON [schema].[tableName]
    FOR UPDATE AS
BEGIN
    <trigger definition>
END')

Procedures

Drop a stored procedure

DROP PROCEDURE IF EXISTS [schema].<procedureName>;

Create a stored procedure

CREATE OR REPLACE <procedureName>

Documentation

View documentation on extended attributes

These queries allow you to see all the documentation on columns and database objects in a single result view for each.

-- Useful queries here: https://www.mssqltips.com/sqlservertip/5384/working-with-sql-server-extended-properties/
--

-- Get column level extended attributes
--
SELECT
    s.name schemaName,
	t.name tableName,
	c.name columnName,
	CAST(
		e.value AS NVARCHAR(MAX)
	) extendedProperties
FROM
	sys.schemas s
	JOIN sys.tables t ON (s.schema_id = t.schema_id)
	JOIN sys.columns c ON t.object_id = c.object_id
	LEFT JOIN sys.extended_properties e ON (t.object_id = e.major_id)
	AND c.column_id = e.minor_id
	AND e.name = 'MS_Description'
ORDER BY
	s.name,
	t.name,
	c.column_id; 
	

-- Get table level extended attributes
--
SELECT
	SCHEMA_NAME(t.schema_id) AS SchemaName,
	t.name AS tableName,
	p.name AS ExtendedPropertyName,
	CAST(p.value AS nvarchar(max)) AS ExtendedPropertyValue
FROM
	sys.tables AS t
	INNER JOIN sys.extended_properties AS p ON p.major_id = t.object_id
	AND p.minor_id = 0
	AND p.class = 1;

Add a comment to a Table

EXEC sys.sp_addextendedproperty @name = N'MS_Description', @value = N'This table does something wonderful...',
     @level0type = N'SCHEMA', @level0name = '<your schema>', @level1type = N'TABLE', @level1name = '<your table name>';

Add a comment to a Column

EXEC sys.sp_addextendedproperty @name = N'MS_Description', @value = 'A wonderful comment about the column.', @level0type = N'Schema',
     @level0name = '<your schema>', @level1type = N'Table', @level1name = '<your table name>', @level2type = N'Column',
     @level2name = '<your col name>';

Remove a comment from a Column

EXEC sys.sp_dropextendedproperty @name = N'MS_Description',
@level0type = N'Schema',
@level0name = '<your schema>',
@level1type = N'Table',
@level1name = '<your table>',
@level2type = N'Column',
@level2name = '<your column name>';

Users

Check to see if a user exists

SELECT
    name AS username,
	create_date,
	modify_date,
	type_desc AS TYPE,
	authentication_type_desc AS authentication_type
FROM
	sys.database_principals
WHERE
	TYPE NOT IN ('A', 'G', 'R', 'X')
	AND sid IS NOT NULL
ORDER BY
	username;

So you can check to see if a user exists before creating it:

IF NOT EXISTS (SELECT [name]
                FROM [sys].[database_principals]
                WHERE [type] = N'S' AND [name] = N'<NEW_USER>')
BEGIN
    CREATE USER [<NEW_USER>] WITH PASSWORD [<PASSWORD>], DEFAULT_SCHEMA=[<SOME_SCHEMA>]
END