Setting your database Compatibility Level to match the SQL Server version

It is not uncommon to have databases with a Compatibility Level that does not match the version of SQL Server they are running on. When you upgrade a SQL Server installation the databases retain a Compatibility Level that matches the version you upgraded from. The same applies to restoring or attaching databases from an earlier version.

I wrote the script below to set the Compatibility Level of a database to match the version of SQL Server. It is designed to work only on SQL Server 2005 and SQL Server 2008 instances. It uses the sys.databases view that does not exist in SQL Server 2000. I decided to use this view because I knew the script would not be executed on a SQL Server 2000 instance.

DECLARE @database nvarchar(128)
SET @database = 'Foo'

DECLARE @databaseLevel tinyint
SELECT @databaseLevel = compatibility_level FROM sys.databases WHERE name = @database
IF @databaseLevel IS NULL
    BEGIN
        PRINT N'The database ''' + @database + ''' does not exist.'
        RETURN
    END

PRINT N'Database Compatibility Level: ' + CONVERT(nvarchar, @databaseLevel)

DECLARE @productVersion nvarchar(128)
SELECT @productVersion = CONVERT(nvarchar(128), SERVERPROPERTY('ProductVersion'))
PRINT N'Server Product Version: ' + @productVersion

DECLARE @majorVersion tinyint
SELECT @majorVersion = CONVERT(tinyint, SUBSTRING(@productVersion, 0, CHARINDEX('.' , @productVersion)))
PRINT N'Server Major Version: ' + CONVERT(nvarchar, @majorVersion)

DECLARE @serverLevel tinyint
SET @serverLevel = @majorVersion * 10
PRINT N'Server Compatibility Level: ' + CONVERT(nvarchar, @serverLevel)

IF @databaseLevel = @serverLevel
    BEGIN
        PRINT N'The Compatibility Level for ''' + @database + ''' already matches the SQL Server version.'
        RETURN
    END

DECLARE @query nvarchar(max)
SET @query = N'ALTER DATABASE [' + @database + '] SET SINGLE_USER'
EXEC sp_executesql @query

EXEC sp_dbcmptlevel @database, @serverLevel
PRINT N'The Compatibility Level for ''' + @database + ''' has been updated.'

SET @query = N'ALTER DATABASE [' + @database + '] SET MULTI_USER'
EXEC sp_executesql @query