sql - 将根据 CASE 语句计算的两列相乘

Question

我正在使用 CASE 语句在 PostgreSQL 中执行 SQL 查询，如下所示:

SELECT
    CASE column1
        WHEN something THEN 10
        ELSE 20
        END AS newcol1
    CASE column12
        WHEN something THEN 30
        ELSE 40
        END AS newcol2
COUNT(column3) newcol3
FROM table
GROUP BY newcol1,newcol2,newcol3

我需要第四列，它必须是 newcol2 * newcol3 的结果，我该怎么做？

如果我把 (newcol2 * newcol3) AS newcol4 我得到一个语法错误。

Answer 1

如果有帮助的话，您始终可以使用 CTE 将事物抽象到不同的级别 - 类似于 ...

With CTE as
(
 SELECT
  CASE column1
    WHEN something THEN 10
    ELSE 20
    END AS newcol1,
  CASE column12
    WHEN something THEN 30
    ELSE 40
    END AS newcol2,
  column3,
 FROM table
)
SELECT
  newcol1, newcol2,
  count(column3) as newcol3,
 (newcol2 * newcol3) AS newcol4
FROM CTE 
GROUP BY newcol1,newcol2,newcol3