Sign Up to our social questions and Answers Engine to ask questions, answer people’s questions, and connect with other people.
Login to our social questions & Answers Engine to ask questions answer people’s questions & connect with other people.
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Please briefly explain why you feel this question should be reported.
Please briefly explain why you feel this answer should be reported.
Please briefly explain why you feel this user should be reported.
I have the following statement:
SELECT CASE WHEN (1 = 1) THEN 10 ELSE dbo.at_Test_Function(5) END AS Result
I just want to confirm that in this case the function wont be executed?
My reason for asking is that the function is particularly slow and if the critiria is true I want to avoid calling the function…
Cheers
Anthony
Do not make this assumption, it is WRONG. The Query Optimizer is completely free to choose the evaluation order it pleases and SQL as a language does NOT offer operator short-circuit. Even if you may find in testing that the function is never evaluated, in production you may hit every now and then conditions that cause the server to choose a different execution plan and first evaluate the function, then the rest of the expression. A typical example would be when the server notices that the function return is deterministic and not depending on the row data, in which case it would first evaluate the function to get the value, and after that start scanning the table and evaluate the WHERE inclusion criteria using the function value determined beforehand.