Question

使用此查询我尝试对SUM函数的结果求和：

select 
DAY(created_at) AS day, 
SUM(if(status = '1', 1, 0)) AS result, 
SUM(if(status = '2', 1, 0)) AS noresult,
SUM(result + noresult)
from `clients` where `doctor_id` = 2 and MONTH(created_at) = MONTH(CURRENT_TIMESTAMP) group by `day`

我尝试在这一行中这样做：

SUM(result + noresult)

Answer 1

试试这个：

select 
    DAY(created_at) AS day, 
    SUM(if(status = '1', 1, 0)) AS result, 
    SUM(if(status = '2', 1, 0)) AS noresult,
    SUM(if(status in ('1', '2'), 1, 0)) 
from `clients` 
where `doctor_id` = 2 and MONTH(created_at) = MONTH(CURRENT_TIMESTAMP) 
group by `day`

Answer 2

您不能在选择列名称中使用别名，您必须重复代码

select 
DAY(created_at) AS day, 
SUM(if(status = '1', 1, 0)) AS result, 
SUM(if(status = '2', 1, 0)) AS noresult,
SUM(if(status = '1', 1, 0)) + SUM(if(status = '2', 1, 0)) AS all_result

from `clients` where `doctor_id` = 2 and MONTH(created_at) = MONTH(CURRENT_TIMESTAMP) group by `day`

你必须重复代码，因为不同的SQL子句按特定的顺序处理（首先从那时开始然后选择和分组......等等）所以在选择解析时，别名不是可用于sql引擎

Answer 3

正如其他几个人所说，你不能在你的select语句中使用别名。但是，为了保持清洁，您可以结合两种条件，而不是将SUM两个字段相加。

select 
DAY(created_at) AS day, 
SUM(if(status = '1', 1, 0)) AS result, 
SUM(if(status = '2', 1, 0)) AS noresult,
SUM(if(status = '1' OR status = '2', 1, 0)) AS newcolumn
from `clients` where `doctor_id` = 2 and MONTH(created_at) = MONTH(CURRENT_TIMESTAMP) group by `day`

如何SUM结果SUMs SQL？

3 个答案: