IsEmpty function like ISNULL in SQL Server?

Please try:

SET @YourValue=ISNULL(NULLIF(@YourValue,' '), NULL)

which returns NULL if value is NULL, empty or space.

Note: NULLIF returns the first expression if the two expressions are not equivalent. If the expressions are equivalent, NULLIF returns a null value of the type of the first expression.

Try NULLIF as below

NULLIF(@SKU,'')