http://sqlblog.com/blogs/john_paul_cook/archive/2013/02/08/union-union-all-and-order-by.aspxAt every client where I've worked, there have always been questions about UNION and UNION ALL. They may return the same results or they may not. It all depends on the data. If you don't have any duplicates, you'll get the same number of rows returnedenCommunityServer 2.1 SP2 (Build: 61129.1)http://sqlblog.com/blogs/john_paul_cook/archive/2013/02/08/union-union-all-and-order-by.aspx#47615Sat, 09 Feb 2013 04:56:16 GMT21093a07-8b3d-42db-8cbf-3350fcbf5496:47615Ian Yates<p>I'm in the habit of using UNION ALL unless I explicitly want the dedupe semantics of UNION specifically because it's faster (as you allude to).</p>