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 to run a SELECT statement across several tables. I am sure the tables return different records. I am anyway using UNION ALL.
Is it better to use UNION or of UNION ALL in performance terms when I am sure the tables return different records?
UNION ALL will perform better than UNION when you’re not concerned about eliminating duplicate records because you’re avoiding an expensive distinct sort operation. See: SQL SERVER – Difference Between Union vs. Union All – Optimal Performance Comparison