Mysql优化（3）索引优化-CFANZ编程社区

Mysql优化（3）索引优化

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2022-06-20

下面我们为表t2创建一个索引：

[SQL] 纯文本查看复制代码

001002003004005006007008009010011	`mysql>` `create``index``in_id` `on``t2(id);``Query OK, 0` `rows``affected (0.01 sec)``Records: 0 Duplicates: 0 Warnings: 0` `mysql> show` `index``from``t2;``+``-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+``\|` `Table``\| Non_unique \| Key_name \| Seq_in_index \| Column_name \| Collation \| Cardinality \| Sub_part \| Packed \|` `Null``\| Index_type \| Comment \|``+``-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+``\| t2 \| 1 \| in_id \| 1 \| id \| A \|` `NULL``\|` `NULL``\|` `NULL``\| YES \| BTREE \| \|``+``-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+``1 row` `in``set``(0.00 sec)`

并插入1000万行的数据。

然后再用：

[SQL] 纯文本查看复制代码

001	`explain` `select``*` `from``t2` `where``id=1;`

或者

[SQL] 纯文本查看复制代码

001	`desc``select``*` `from``t2` `where``id=1;`

查询其影响行数。决定其是否需要优化

http://www.sodu666.com/ZhuShenQi/

http://tieba.sodu666.com/

下面我们为表t2创建一个索引：

[SQL] 纯文本查看复制代码

001002003004005006007008009010011	`mysql>` `create``index``in_id` `on``t2(id);``Query OK, 0` `rows``affected (0.01 sec)``Records: 0 Duplicates: 0 Warnings: 0` `mysql> show` `index``from``t2;``+``-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+``\|` `Table``\| Non_unique \| Key_name \| Seq_in_index \| Column_name \| Collation \| Cardinality \| Sub_part \| Packed \|` `Null``\| Index_type \| Comment \|``+``-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+``\| t2 \| 1 \| in_id \| 1 \| id \| A \|` `NULL``\|` `NULL``\|` `NULL``\| YES \| BTREE \| \|``+``-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+``1 row` `in``set``(0.00 sec)`

并插入1000万行的数据。

然后再用：

[SQL] 纯文本查看复制代码

001	`explain` `select``*` `from``t2` `where``id=1;`

或者

[SQL] 纯文本查看复制代码

001	`desc``select``*` `from``t2` `where``id=1;`

查询其影响行数。决定其是否需要优化

http://www.sodu666.com/ZhuShenQi/

http://tieba.sodu666.com/

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