What is the Compatibility level of SQL Server?

To know the current compatibility_level of your database you can run you should follow the below-given advice: SELECT name,compatibility_level FROM sys.databases WHERE name = 'DatabaseName'; Result for my TEST database: name compatibility_level TEST 140 If the compatibility level changes, for example with the command: ALTER DATABASE TEST SET COMPATIBILITY_LEVEL = 120; You could find the date and time that happened in the SQL Server error log: Or reading the (current) error log file with xp_readerrorlog: EXEC sp_readerrorlog 0, 1, 'COMPATIBILITY_LEVEL' Result  Replace the first parameter of xp_readerrorlog with 1 to read the second error log file, 2 for the third file.