如何SUM結果兩個SUM SQL？

Question

使用此查詢我試着總結兩個SUM函數的結果：

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` 

我嘗試這樣做，在這條線：

SUM(result + noresult) 

Answer 1

其他幾個人都表示，你不能在你的SELECT語句中使用別名。但是，爲了保持清潔，您可以結合這兩種情況，而不是總結SUM這兩個字段。

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` 

Answer 2

不能在選擇列使用別名，你必須重複代碼

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` 

必須重複代碼，因爲不同的SQL子句以特定順序處理（首先從那裏再然後通過選擇和和組....等），所以在選擇解析別名的時刻不可用於SQL引擎

Answer 3

試試這個：

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`