MySQL indexes - what are the best practises?

Posted by Haroldo on Stack Overflow See other posts from Stack Overflow or by Haroldo
Published on 2010-06-15T21:39:07Z Indexed on 2010/06/15 21:42 UTC
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php

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mysql

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best-practices

I've been using indexes on my mysql databases for a while now but never properly learnt about them. Generally I put an index on any fields that i will be searching or selecting using a WHERE clause but sometimes it doesn't seem so black and white.

What are the best practises for mysql indexes?

example situations/dilemas:

If a table has six columns and all of them are searchable, should i index all of them or none of them?

.

What are the negetive performance impacts of indexing?

.

If i have a VARCHAR 2500 column which is searchable from parts of my site, should i index it?

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