如何在具有多列的MySQL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);
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable612 values(10,20,1000); mysql> insert into DemoTable612 values(30,40,500); mysql> insert into DemoTable612 values(50,70,1200); mysql> insert into DemoTable612 values(100,120,400);
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)