MySQL 查询如何为表中的值设置不同的组合?
mysqlmysqli database
首先我们创建一个表 −
mysql> create table DemoTable622 (Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,Value1 int,Value2 int); Query OK, 0 rows affected (1.08 sec)
使用 insert 命令在表中插入一些记录 −
mysql> insert into DemoTable622(Value1,Value2) values(1000,1000); Query OK, 1 row affected (0.23 sec) mysql> insert into DemoTable622(Value1,Value2) values(2000,3000); Query OK, 1 row affected (1.04 sec)
使用 select 语句显示表中的所有记录 −
mysql> select *from DemoTable622;
这将产生以下输出 −
+----+--------+--------+ | Id | Value1 | Value2 | +----+--------+--------+ | 1 | 1000 | 1000 | | 2 | 2000 | 3000 | +----+--------+--------+ 2 rows in set (0.00 sec)
这是对 MySQL 组合的查询 −
mysql> select tbl1.Id,tbl2.Value1,tbl3.Value2 from DemoTable622 tbl1,DemoTable622 tbl2,DemoTable622 tbl3;
这将产生以下输出 −
+----+--------+--------+ | Id | Value1 | Value2 | +----+--------+--------+ | 1 | 1000 | 1000 | | 2 | 1000 | 1000 | | 1 | 2000 | 1000 | | 2 | 2000 | 1000 | | 1 | 1000 | 3000 | | 2 | 1000 | 3000 | | 1 | 2000 | 3000 | | 2 | 2000 | 3000 | +----+--------+--------+ 8 rows in set (0.01 sec)
