MySQL 如何在删除一些行后优化MySQL表

使用OPTIMIZE TABLE命令来优化MySQL表 –

optimize table yourTableName;

首先让我们创建一个表 –

mysql> create table DemoTable(
   Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
   Name varchar(100)
);
Query OK, 0 rows affected (1.38 sec)

使用插入命令向表中插入一些记录 –

mysql> insert into DemoTable(Name) values('Chris');
Query OK, 1 row affected (0.27 sec)
mysql> insert into DemoTable(Name) values('Robert');
Query OK, 1 row affected (0.15 sec)
mysql> insert into DemoTable(Name) values('Bob');
Query OK, 1 row affected (0.22 sec)
mysql> insert into DemoTable(Name) values('David');
Query OK, 1 row affected (0.38 sec)

使用SELECT语句显示表中的所有记录 –

mysql> select * from DemoTable;

这将产生以下输出 –

+----+--------+
| Id | Name   |
+----+--------+
|  1 | Chris  |
|  2 | Robert |
|  3 | Bob    |
|  4 | David  |
+----+--------+
4 rows in set (0.00 sec)

现在让我们从表中删除行 –

mysql> delete from DemoTable where Id IN(1,3);
Query OK, 2 rows affected (0.29 sec)
mysql> select *from DemoTable;
+----+--------+
| Id | Name   |
+----+--------+
|  2 | Robert |
|  4 | David  |
+----+--------+
2 rows in set (0.00 sec)

以下是优化上面创建的表并删除一些行之后的查询 –

mysql> optimize table DemoTable;

这将产生以下输出 –

+------------------+----------+----------+-------------------------------------------------------------------+
| Table            | Op       | Msg_type | Msg_text                                                          |
+------------------+----------+----------+-------------------------------------------------------------------+
| web.DemoTable    | optimize | note     | Table does not support optimize, doing recreate + analyze instead |
| web.DemoTable    | optimize | status   | OK                                                                |
+------------------+----------+----------+-------------------------------------------------------------------+
2 rows in set (4.32 sec)