Moreover, a simple SELECT into a variable without a table is optimized as equivalent to a SET, so in the following example, only the third variation returns the expected NULL:

DECLARE @SetOpt INT, @SelOpt INT, @SetSelOpt INT

Set FMTONLY ON;

SET @SetOpt = @@OPTIONS

SELECT @SelOpt = @@OPTIONS

SET @SetSelOpt = (SELECT @@OPTIONS)

Set FMTONLY OFF;

SELECT @SetOpt AS SetOpt, @SelOpt AS SelOpt, @SetSelOpt AS SetSelOpt

Therefore, for maximum readability and predictability, I now use @t.ovod-everett simple suggestion:

DECLARE @NullIfFmtOnly INT = (SELECT 1);

or if you need it to work in 2005 and earlier:

DECLARE @NullIfFmtOnly INT SET @NullIfFmtOnly = (SELECT 1)