mysql LIKE占两倍 [英] mysql LIKE with double percent

问题描述

我只是调试旧版代码，但发现其中有一个奇怪的部分.有人知道吗，MYSQL字符串中的以下含义是什么?

I just debugging a legacy code and I found a strange part in it. Does anybody has an idea, what does the following mean in the MYSQL string?

full_name LIKE '%%{fullname}%%'

推荐答案

正如Mihir Dave的注释链接所指向的答案一样，如果传递%%而不是%，则SQL不会有任何区别.由于单个%匹配零个或多个字符，因此%%中的每个元字符也将匹配零个或多个，并且最终同一字符串将以一种或另一种方式匹配.

As in the answer Mihir Dave's comment links to, there's no difference to SQL if you pass %% instead of %. Since a single % matches zero or more characters, then each of the metacharacters in %% would also match zero or more, and ultimately the same string would match one way or another.

但是我想您的遗留代码是Python 2.6之前的版本，它使用%作为字符串格式的元字符，并且您必须像%%一样将其加倍以获取单个文字%字符.

But I'd guess your legacy code is pre-Python 2.6 that uses % as a metacharacter in string formatting, and you have to double it like %% to get a single literal % character.

另请参阅:

• 如何在Python中有选择地转义百分比(％)字符串?
• https://docs.python.org/2.6/library/stdtypes.html#string-formatting-operations

• How can I selectively escape percent (%) in Python strings?
• https://docs.python.org/2.6/library/stdtypes.html#string-formatting-operations

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