通过使用MySQL IF语句和用户定义变量中的SELECT来设置自定义消息
让我们首先创建一个表-
mysql> create table DemoTable2008 ( Value int );
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable2008 values(10); mysql> insert into DemoTable2008 values(20); mysql> insert into DemoTable2008 values(30); mysql> insert into DemoTable2008 values(-31); mysql> insert into DemoTable2008 values(-28);
使用select语句显示表中的所有记录-
mysql> select * from DemoTable2008;
这将产生以下输出-
+-------+ | Value | +-------+ | 10 | | 20 | | 30 | | -31 | | -28 | +-------+ 5 rows in set (0.00 sec)
这是首先使用用户定义的变量并将输入作为SELECT的查询-
mysql> set @value:=(select sum(Value) from DemoTable2008); mysql> select if(@value > 0, 'Value is greater than 0','Not greater than') as Result;
这将产生以下输出-
+-------------------------+ | Result | +-------------------------+ | Value is greater than 0 | +-------------------------+ 1 row in set (0.00 sec)