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DISTINCT vs GROUP BY [message #1319] Sat, 26 May 2007 01:34 Go to previous message
mysql_beginner is currently offline mysql_beginner
Messages: 5
Registered: May 2007
Junior Member
Is there any performance difference between DISTINCT and GROUP BY?

I have a table articles and I want to get unique users who posted the articles. userid has an index. What should I use DISTINCT or GROUP BY? Is there any difference between their performance? I am concerned about the performance.

I need to get only userid from articles. Which one is better?
SELECT DISTINCT userid FROM articles WHERE posted_date BETWEEN '2007-01-01' AND CURDATE();

OR
SELECT userid FROM articles WHERE posted_date BETWEEN '2007-01-01' AND CURDATE() GROUP BY userid;


EXPLAIN is exactly the same for both.
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