如何在MySQL的单个表中优化许多SELECT？
要优化许多SELECT，请使用一次并应用于IN()获取多个值。让我们首先创建一个表-
mysql> create table DemoTable ( Id int, Name varchar(100), Age int );
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable values(1,'Chris',23); mysql> insert into DemoTable values(2,'David',21); mysql> insert into DemoTable values(3,'Mike',24); mysql> insert into DemoTable values(4,'Robert',22);
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 | Age | +------+--------+------+ | 1 | Chris | 23 | | 2 | David | 21 | | 3 | Mike | 24 | | 4 | Robert | 22 | +------+--------+------+ 4 rows in set (0.00 sec)
以下是在单个表上优化许多SELECT的查询-
mysql> select Name from DemoTable where Age in(21,22,23);
这将产生以下输出-
+--------+ | Name | +--------+ | Chris | | David | | Robert | +--------+ 3 rows in set (0.00 sec)