IN()

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High Performance My SQL, Third Edition

Consider the followingWHERE clause:

WHERE eye_color IN(‘brown‘,‘blue‘,‘hazel‘)
AND hair_color IN(‘black‘,‘red‘,‘blonde‘,‘brown‘)
AND sex IN(‘M‘,‘F‘)

The optimizer will convert this into 4*3*2 = 24 combinations, and the W
HERE clause will then have to check for each of them.

IN()

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原文地址：http://www.cnblogs.com/yuanjiangw/p/6214352.html