极客教程MySQL 如何提高查询速度
为了更快地查询，使用MySQL IN()，因为它内部使用索引。让我们首先创建一个表 –
mysql> create table DemoTable1618
-> (
-> ClientId int NOT NULL AUTO_INCREMENT PRIMARY KEY,
-> ClientName varchar(20),
-> ClientEmailId varchar(30)
-> );
Query OK, 0 rows affected (1.53 sec)
使用插入命令在表中插入一些记录：
mysql> insert into DemoTable1618(ClientName,ClientEmailId) values('Chris Brown','Brown323@gmail.com');
Query OK, 1 row affected (0.15 sec)
mysql> insert into DemoTable1618(ClientName,ClientEmailId) values('David Miller','MillerDavid@gmail.com');
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable1618(ClientName,ClientEmailId) values('John Doe','998John_Doe@gmail.com');
Query OK, 1 row affected (0.28 sec)
mysql> insert into DemoTable1618(ClientName,ClientEmailId) values('John Smith','999John_Smith@gmail.com');
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable1618(ClientName,ClientEmailId) values('Adam Smith','Adam_Smith@gmail.com');
Query OK, 1 row affected (0.17 sec)
使用选择语句从表中显示所有记录 –
mysql> select * from DemoTable1618;
这将产生以下输出 –
+----------+--------------+-------------------------+
| ClientId | ClientName | ClientEmailId |
+----------+--------------+-------------------------+
| 1 | Chris Brown | Brown323@gmail.com |
| 2 | David Miller | MillerDavid@gmail.com |
| 3 | John Doe | 998John_Doe@gmail.com |
| 4 | John Smith | 999John_Smith@gmail.com |
| 5 | Adam Smith | Adam_Smith@gmail.com |
+----------+--------------+-------------------------+
5 rows in set (0.00 sec)
以下是使用IN()进行更快查询的查询 –
mysql> select * from DemoTable1618 where ClientEmailId IN('998John_Doe@gmail.com','999John_Smith@gmail.com','MillerDavid@gmail.com');
这将产生以下输出 –
+----------+--------------+-------------------------+
| ClientId | ClientName | ClientEmailId |
+----------+--------------+-------------------------+
| 2 | David Miller | MillerDavid@gmail.com |
| 3 | John Doe | 998John_Doe@gmail.com |
| 4 | John Smith | 999John_Smith@gmail.com |
+----------+--------------+-------------------------+
3 rows in set (0.00 sec)
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