ConFoo Montreal 2026: Call for Papers

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ASchmidt at Anamera dot net
4 years ago
Caution when escaping the % and _ wildcard characters. According to an often overlooked note at the bottom of:

https://dev.mysql.com/doc/refman/5.7/en/string-literals.html#character-escape-sequences

the escape sequences \% and \_ will ONLY be interpreted as % and _, *if* they occur in a LIKE! (Same for MySQL 8.0)

In regular string literals, the escape sequences \% and \_ are treated as those two character pairs. So if those escape sequences appear in a WHERE "=" instead of a WHERE LIKE, they would NOT match a single % or _ character!

Consequently, one MUST use two "escape" functions: The real-escape-string (or equivalent) for regular string literals, and an amended escape function JUST for string literals that are intended to be used in LIKE.

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