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Snailclimb merged 1 commit into from
Feb 28, 2023
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Update mysql-index.md #1932

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2 changes: 1 addition & 1 deletion docs/database/mysql/mysql-index.md
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Expand Up @@ -278,7 +278,7 @@ SELECT id FROM table WHERE id=1;
索引失效也是慢查询的主要原因之一，常见的导致索引失效的情况有下面这些：

- 使用 `SELECT *` 进行查询;
- 创建了组合索引，但查询条件未准守最左匹配原则;
- 创建了组合索引，但查询条件未遵守最左匹配原则;
- 在索引列上进行计算、函数、类型转换等操作;
- 以 `%` 开头的 LIKE 查询比如 `like '%abc'`;
- 查询条件中使用 or，且 or 的前后条件中有一个列没有索引，涉及的索引都不会被使用到;
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