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Legal Studies如何将正值转换为负值，同时插入 MySQL？
我们首先创建一个表
mysql> create table recordsDemo -> ( -> UserId int, -> Value int -> ); Query OK, 0 rows affected (0.52 sec)
现在使用插入命令在表中插入一些记录。
查询如下
mysql> insert into recordsDemo values(1,10); Query OK, 1 row affected (0.17 sec) mysql> insert into recordsDemo values(3,598); Query OK, 1 row affected (0.18 sec) mysql> insert into recordsDemo values(5,786); Query OK, 1 row affected (0.25 sec) mysql> insert into recordsDemo values(7,189); Query OK, 1 row affected (0.16 sec) mysql> insert into recordsDemo values(9,345); Query OK, 1 row affected (0.14 sec)
使用选择语句显示表中的所有记录。
查询如下
mysql> select *from recordsDemo;
以下是输出
+--------+-------+ | UserId | Value | +--------+-------+ | 1 | 10 | | 3 | 598 | | 5 | 786 | | 7 | 189 | | 9 | 345 | +--------+-------+ 5 rows in set (0.00 sec)
创建一个第二个表。创建第二个表的查询如下
mysql> create table PositiveToNegativeValueDemo -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Money int -> ); Query OK, 0 rows affected (0.83 sec)
以下是如何在插入时将正值转换为负值
mysql> insert into PositiveToNegativeValueDemo(Id,Money) -> select UserId,(-1*Value) from recordsDemo; Query OK, 5 rows affected (0.15 sec) Records: 5 Duplicates: 0 Warnings: 0
现在使用选择语句检查表中的记录。
查询如下
mysql> select *from PositiveToNegativeValueDemo;
以下是输出
+------+-------+ | Id | Money | +------+-------+ | 1 | -10 | | 3 | -598 | | 5 | -786 | | 7 | -189 | | 9 | -345 | +------+-------+ 5 rows in set (0.00 sec)
更新时间：30-Jul-2019
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