Mysql Query error: BIGINT UNSIGNED value is out of range in..解决方法（转）

原文：https://blog.51cto.com/bstdn/1951064

1、问题

• 当字段类型为 unsigned 时，使用相关结果为负值时就会报错，报错如下：

BIGINT UNSIGNED value is out of range in ..1.

2、解决

• 使用 cast() 修改字段类型为 signed

select cast(quantity as signed) - cast(quantity2 as signed) from order_details