在同一个select语句中聚合查询

Question

我有一个select语句，它返回5列（需要1-2分钟） 其中一列是颜色（即只有红色，蓝色和黄色三种颜色）。现在我想在同一个select语句中显示具有Red的行数，具有Blue的行数和具有黄色的行数。

Select语句是这个

我想要像这样输出

任何帮助？

Answer 1

你想要这个（对于SQL Server 2005 +）：

SELECT  *, SUM(CASE WHEN Color = 'RED' THEN 1 ELSE 0 END) OVER() [RED],
        SUM(CASE WHEN Color = 'BLUE' THEN 1 ELSE 0 END) OVER() [BLUE],
        SUM(CASE WHEN Color = 'Yellow' THEN 1 ELSE 0 END) OVER() [Yellow]
FROM YourTable

Answer 2

使用CTE（公用表格表达式）：

; 
WITH cte AS
( SELECT ...
  ... your query here
) 
WITH grp AS
( SELECT 
        color
      , COUNT(*) AS cnt
  FROM
        cte
  GROUP BY
        color
) 
SELECT 
      cte.*
    , (SELECT cnt FROM grp WHERE color = 'Red')    AS Red
    , (SELECT cnt FROM grp WHERE color = 'Blue')   AS Blue
    , (SELECT cnt FROM grp WHERE color = 'Yellow') AS Yellow
FROM 
      cte