MySQL：AND是有条件的还是逻辑的？ [英] MySQL: is AND conditional or logical?

问题描述

如果我在MySQL中运行这样的查询：

If I run such a query in MySQL:

SELECT field FROM table WHERE field1=42 AND field2 LIKE '%beer%';

将对每一行进行解析，因为在 field2中有啤酒 还是仅其 field1 = 42的那些？

Will every row be parsed for having "beer" in field2 or only those whose field1=42?

推荐答案

这取决于查询计划以及表上的索引。尝试在查询前放置 EXPLAIN ，MySQL会告诉您更多信息。不过一般来说，如果对 field1 建立索引，则仅对 LIKE > field1 是42。

That depends on the query plan and what indexes you have on the table. Try putting EXPLAIN before your query and MySQL will tell you more. Generally speaking though, if field1 is indexed, then LIKE should only be performed for those rows where field1 is 42.

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