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修正关于 OR 导致索引失效的描述 #298

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修正关于 OR 导致索引失效的描述 #298

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2 changes: 1 addition & 1 deletion mysql/index/index_lose.md
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Expand Up @@ -301,7 +301,7 @@ MySQL 5.5 的话，前面 a 会走索引，在联合索引找到主键值后，

## WHERE 子句中的 OR

在 WHERE 子句中，如果在 OR 前的条件列是索引列，而在 OR 后的条件列不是索引列，那么索引会失效。
在 WHERE 子句中，如果 OR 前后的条件列中存在一个列没有创建索引，就会导致整个查询语句索引失效。

举个例子，比如下面的查询语句，id 是主键，age 是普通列，从执行计划的结果看，是走了全表扫描。

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