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Re: how to optimise query for 10+ millions records
Posted by: Rick James
Date: February 11, 2012 11:26PM

Need some details; please provide
* SHOW CREATE TABLE tbl\G -- engine, indexes
* SHOW TABLE STATUS LIKE 'tbl'\G -- sizes
* EXPLAIN SELECT ...\G -- clues of inefficiencies
* SHOW VARIABLES LIKE '%buffer%'; -- cache size
and surround them with [ code ] and [ / code ]
How much RAM do you have?

We will probably focus on the LIKE. Some things to note:
* If @l_Destination begins with a wildcard (% or _), the index will be useless.
* Taking a function (in your case: "IFNULL(...)") of a column makes it impossible to use an index on that column.

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Re: how to optimise query for 10+ millions records
February 11, 2012 11:26PM

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