Index-is-useless-when-use-function-on-indexed-field.md

• Date : 2015-12-01
• Tags : #mysql #sql #index

Index is useless when use function on indexed field

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

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

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

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