#TIL : Index is useless when use function on indexed field

Reality, if using function on indexed field, you will broke indexing by accident.
Eg:

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WHERE MONTH(`date`) = 11 AND YEAR(`date`) = 2015

Solution is transform the query to comparison query, like this :

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WHERE `date` >= '2015-11-01' AND `date` < '2015-12-01'