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Tag Archives: distinct

mySQL: OR, UNION and UNION ALL

I was doing some SQL tuning on mySQL today and I learned a few interesting things. Let’s take an example of a simple query where we have an OR of two mutually exclusive conditions, each on indexed columns. SELECT * FROM   t1 WHERE  user_id = 1 OR     location_id = 2; In mySQL there is a [...]

Posted 22 July 2010 † Tim... § Oracle ‡ Comments (0) ° Also tagged: , ,