Question

我希望您提供有关我在单个查询中无法获得的查询的帮助。

Table timeaccount

Field   Type
id      mediumint(8)   --> Primary key autoincrement
user    varchar(40)    --> user, e.g. 'john.fisher'
type    varchar(15)    --> can only be 'SUM' or 'SUBSTRACT'
minutes smallint(5)    --> an amount of minutes

这表示工人的时间会计，其中每个记录表示工人（字段“用户”）已从其余额中添加或减少了多少分钟（根据字段“类型”）。

我只想在一个查询中获得来自特定工作者的余额，在伪sql中它将是：

select sum(minutes) from timeaccount where worker = 'john.fisher' and type = 'SUM'
-
select sum(minutes) from timeaccount where worker = 'john.fisher' and type = 'SUBSTRACT'

as balance

感谢您的帮助，

Answer 1

SELECT
  SUM(IF(type = 'SUM', minutes, 0)) -
  SUM(IF(type = 'SUBTRACT', minutes, 0)) AS balance
FROM timeaccount
WHERE worker = 'john.fisher'

Answer 2

可替换地：

SELECT SUM(minutes * case type when 'SUBTRACT' then -1 else 1 end) AS balance
FROM timeaccount
WHERE worker = 'john.fisher' and type in ('SUM','SUBTRACT')

Answer 3

SELECT (SUM_VAL - SUBSTRACT_VAL) as balance FROM
(
 select sum(minutes) AS SUM_VAL FROM timeaccount WHERE worker = 'john.fisher' AND type =     'SUM', 
 select sum(minutes) AS SUBSTRACT_VAL FROM timeaccount WHERE worker = 'john.fisher' AND type = 'SUBSTRACT'
) t1

Answer 4

试试这个：

select sum(if(type = 'SUM', minutes, 0)) - sum(if(type = 'SUBSTRACT', minutes, 0)) as balance from timeaccount where worker = 'john.fisher'

从同一个表中减去两个SUM

4 个答案: