Peter,

What you have explained over there is wrong.

If you run this one, it will execute succesfully.

IF NOT EXISTS(SELECT 1 FROM sys.server_principals b

WHERE b.sid=(SELECT b.sid FROM sys.databases a WHERE a.name=DB_NAME()))

BEGIN

PRINT N'Invalid Database Owner'

END

ELSE

BEGIN

PRINT N'Valid Database Owner'

END

But if you run

IF NOT EXISTS(SELECT 1 FROM sys.server_principals b

WHERE b.sid=(SELECT a.sid FROM sys.databases a WHERE a.name=DB_NAME()))

BEGIN

PRINT N'Invalid Database Owner'

END

ELSE

BEGIN

PRINT N'Valid Database Owner'

END

It would not run and hence as Hugo said your concept was wrong.