SQL限制選擇查詢

Question

一個專欄中，我想限制爲count(rm_ca) as office列的結果是rm_ca ='1'
我不能投入where條款這是我不希望限制其他領域。只有那一列。如何才能做到這一點？

SELECT count(distinct bl) as bld, 
     count(rm) as rooms, 
     sum(area) as total_area, 
     count(rm_ca) as office 
FROM table 
WHERE dp= '345'; 

Answer 1

用途：

SUM(CASE WHEN rm_ca = 1 THEN 1 ELSE 0 END) AS office 

Answer 2

用途：

SELECT count(distinct bl) as bld, 
    count(rm) as rooms, 
    sum(area) as total_area, 
    count(decode (rm_ca,1,0)) as office 
    FROM table 
    WHERE dp= '345'; 

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