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MySQL JOIN Clause

Posted on 2014-12-03
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Last Modified: 2014-12-03
Scenario:  I have two MySQL tables.  Both of them have an index on the column called "foo."  

1. I run a SELECT query and use a JOIN clause naming "foo" in the two tables.  I get a results set giving the intersection of the tables on "foo."

2. I remove the index from one or both of the tables and rerun the query in #1.

Will I get the same results set from the second (unindexed) SELECT?  Or does the presence of an index affect the results of JOIN?
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Question by:Ray Paseur
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JEaston earned 250 total points
ID: 40478242
If I understand your question correctly, then Yes you should get the same result regardless of whether the joined columns are indexed or not.  Indexed columns are likely to result in a faster query run time - but if the tables are not large then chances are you will not notice the difference.
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by:Guy Hengel [angelIII / a3]
Guy Hengel [angelIII / a3] earned 250 total points
ID: 40478254
I agree 100%: the presence of indexes will not change the data returned, only the speed
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by:Ray Paseur
ID: 40478269
Thanks, colleagues!
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