Database Compatibility Level Option
The Transact-SQL sp_dbcmptlevel system stored procedure can be used to set certain database behavior to be compatible with a specified earlier version of Microsoft SQL Server.
A special rule applies to the relationship among the database compatibility level option, the CONCAT_NULL_YIELDS_NULL database option, and the CONCAT_NULL_YIELDS_NULL SET option. The settings of both options are ignored when the value of compatibility level is for a release earlier than SQL Server version 7.0.
The compatibility level affects the behavior only in the specified database and not the whole server. For more information, see sp_dbcmptlevel (Transact-SQL).