Generate and change all SQL databases to a different compatibility level - Alter SQL Compatibility Level

SELECT name, compatibility_level  

FROM sys.databases where compatibility_level not in(120) -- SQL Server 2012 compatibility_level is 120

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SELECT name, compatibility_level  

FROM sys.databases 

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/* Start Of Code */

DECLARE @SQL VARCHAR(max)  = ''

,             @CompLevel int = 120 -- Need to change the compatibility_level as per SQL Server version

SELECT @SQL += 'ALTER DATABASE ' + quotename(NAME) + ' SET COMPATIBILITY_LEVEL = ' + cast(@CompLevel as char (3)) + ';' + CHAR(10) + CHAR(13)

FROM sys.databases

WHERE 

--COMPATIBILITY_LEVEL not in(120) 

--and 

 compatibility_level <> @CompLevel

PRINT @SQL

--EXEC (@SQL)

/* End Of Code */