MySQL 如何在具有多个列的表中创建条件

对于条件，请使用IF（）。以下是语法 −

IF(yourCondition, trueStatement,falseStatement);

让我们首先创建一个表 −

mysql> create table DemoTable612 (Number1 int,Number2 int,Score int);Query OK, 0 rows affected (0.47 sec)

使用插入命令将一些记录插入表中 −

mysql> insert into DemoTable612 values(10,20,1000);Query OK, 1 row affected (0.12 sec)mysql> insert into DemoTable612 values(30,40,500);Query OK, 1 row affected (0.19 sec)mysql> insert into DemoTable612 values(50,70,1200);Query OK, 1 row affected (0.15 sec)mysql> insert into DemoTable612 values(100,120,400);Query OK, 1 row affected (0.16 sec)

使用select语句显示表中的所有记录 −

mysql> select *from DemoTable612;

这将产生以下输出 −

+---------+---------+-------+| Number1 | Number2 | Score |+---------+---------+-------+|      10 |      20 |  1000 ||      30 |      40 |   500 ||      50 |      70 |  1200 ||     100 |     120 |   400 |+---------+---------+-------+4 rows in set (0.00 sec)

这是在MySQL中创建条件的查询−

mysql> select *,If(Score > 500, Number1*Number2,Number1+Number2) AS Result from DemoTable612;

这将产生以下输出−

+---------+---------+-------+--------+| Number1 | Number2 | Score | Result ||         |         |       |        ||      10 |      20 |  1000 |    200 ||      30 |      40 |   500 |     70 ||      50 |      70 |  1200 |   3500 ||     100 |     120 |   400 |    220 |+---------+---------+-------+--------+4 rows in set (0.00 sec)