如何对两个SUM SQL求和？

Question

Using this query I try to sum result of both SUM function:

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`

I try to do that in this line:

SUM(result + noresult)

Answer 1

Try this:

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

You can't use alias in select columns name you must repeat the code

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`

you must repeat the code because the different SQL clause are processed in a specific order (first from then where then select and and group by .... etc.. ) so at the moment of the select parsing the alias are not available to the sql engine

Answer 3

As several other people have stated, you cannot use aliases in your select statement. However, to keep it cleaner, you could combine both conditions rather than summing both SUM fields.

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`