鴻溝兩列進組由功能SQL

Question

如果我有以下選擇查詢：

select col1, col2, col3, sum(value1) as col4, col5 
from table1 
group by col1, col2, col3, col5 

如何添加COL6 = COL4/COL5？

Answer 1

您無法訪問SELECT子句中的別名。所以，你必須重複sum(value1)：

select col1, col2, col3, 
     sum(value1) as col4, 
     col5, 
     sum(value1)/col5 as col6 
from table1 
group by col1, col2, col3, col5 

Answer 2

您可以在select語句中執行操作。但是，您不能在其中使用SQL語句的別名。所以你需要再次對col4進行計算。只需添加sum(value1)/col5 as col6。

select col1, col2, col3, sum(value1) as col4, col5, sum(value1)/col5 as col6 
from table1 
group by col1, col2, col3, col5 

Answer 3

執行GROUP BY在派生表：

select col1, col2, col3, col4, col5, col4/col5 as col6 
from 
(
    select col1, col2, col3, sum(value1) as col4, col5 
    from table1 
    group by col1, col2, col3, col5 
) dt