SQL Server Compatibility Level

Sets Transact-SQL and query processing behaviors to be compatible with the specified version of the SQL Server Database Engine. 

EXEC dbo.sp_dbcmptlevel @dbname=N'Database01', @new_cmptlevel=90

ALTER DATABASE Database01
SET COMPATIBILITY_LEVEL = 90

Product	Database Engine Version	Default Compatibility Level Designation	Supported Compatibility Level Values
SQL Server 2019 preview	15	150	150, 140, 130, 120, 110, 100
SQL Server 2017 (14.x)	14	140	140, 130, 120, 110, 100
Azure SQL Database single database/elastic pool	12	140	150, 140, 130, 120, 110, 100
Azure SQL Database managed instance	12	140	150, 140, 130, 120, 110, 100
SQL Server 2016 (13.x)	13	130	130, 120, 110, 100
SQL Server 2014 (12.x)	12	120	120, 110, 100
SQL Server 2012 (11.x)	11	110	110, 100, 90
SQL Server 2008 R2	10.5	100	100, 90, 80
SQL Server 2008	10	100	100, 90, 80
SQL Server 2005 (9.x)	9	90	90, 80
SQL Server 2000	8	80	80

Sources:

https://docs.microsoft.com/en-us/sql/t-sql/statements/alter-database-transact-sql-compatibility-level?view=sql-server-2017

https://docs.microsoft.com/en-us/sql/relational-databases/system-stored-procedures/sp-dbcmptlevel-transact-sql?view=sql-server-2017