如何增强我的选择查询以使其在MySQL中更快？
为了更快地查询，请使用MySQL，IN()因为它在内部使用索引。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)
-> );使用insert命令在表中插入一些记录：
mysql> insert into DemoTable1618(ClientName,ClientEmailId) values('Chris Brown','Brown323@gmail.com');
mysql> insert into DemoTable1618(ClientName,ClientEmailId) values('David Miller','MillerDavid@gmail.com');
mysql> insert into DemoTable1618(ClientName,ClientEmailId) values('John Doe','998John_Doe@gmail.com');
mysql> insert into DemoTable1618(ClientName,ClientEmailId) values('John Smith','999John_Smith@gmail.com');
mysql> insert into DemoTable1618(ClientName,ClientEmailId) values('Adam Smith','Adam_Smith@gmail.com');使用select语句显示表中的所有记录-
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)
这是IN()用于更快查询的查询-
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)