SQL有一個回報時的平均回報率= 0

Question

我試圖找到4個回報的平均值a，b，c，d。有時候，一個回報前A = 0，我想省略此唯一發現只有A，B的平均，C

SELECT SUM(CASE WHEN x > 0 THEN COALESCE(a, 0) + COALESCE(b, 0) + COALESCE(c, 0) + COALESCE(d, 0))/4 

請幫助！

Answer 1

Select Z.PrimaryKeyCol, Avg(Z.Value) 
From (
     Select PrimaryKeyCol, a As Value 
     Union All Select PrimaryKeyCol, b 
     Union All Select PrimaryKeyCol, c 
     Union All Select PrimaryKeyCol, d 
     ) As Z 
Where Z.Value <> 0 
Group By Z.PrimaryKeyCol 

Answer 2

select (a+b+c+d) 
/
(if(a = 0,0,1) + if(b = 0,0,1) + if(c = 0,0,1) + if(d = 0,0,1)) 
from table