让我们首先创建一个表-
mysql> create table DemoTable -> ( -> Value int -> );
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable values(10); mysql> insert into DemoTable values(20); mysql> insert into DemoTable values(100);
使用select语句显示表中的所有记录-
mysql> select *from DemoTable;
输出结果
这将产生以下输出-
+-------+ | Value | +-------+ | 10 | | 20 | | 100 | +-------+ 3 rows in set (0.00 sec)
这是在SELECT上将无符号int乘以-1的查询-
mysql> select cast(Value*-1 as signed) from DemoTable;
输出结果
这将产生以下输出-
+--------------------------+ | cast(Value*-1 as signed) | +--------------------------+ | -10 | | -20 | | -100 | +--------------------------+ 3 rows in set (0.00 sec)