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sql - 如果至少存在一个值，则获取计数列 - SQL

问题描述

如果 group by 子句中至少存在一个值，如何为每种颜色创建单独的列？每个颜色列是否需要一个带有 group by 子句的单独 select 语句。提前致谢。

例如

    SELECT
    COUNT(ColorID) AS IcdCodecount,
    Colorname
    -- Blue -> if at least one value exists in 1, 10, 12
    -- Red -> if at least one value in 0, 3, 4, 15
    -- White -> if at least one value in  11, 12, 13, 14
    -- Yellow -> if at least one value in 20, 21, 22, 23
    FROM
      TestTable
    WHERE ColorID IN (
                      1, 10, 12, -- blue
                      0, 3, 4, 15, -- Red
                      11, 12, 13, 14, -- White
                      20, 21, 22, 23, -- yellow)
    GROUP BY Colorname

标签： sql

解决方案

您可以使用条件聚合：

(case when sum(case when colorId in (1, 10, 12) then 1 else 0 end)  > 0 then 1 else 0 end) as is_blue,
(case when sum(case when colorId in (0, 3, 4, 15) then 1 else 0 end)  > 0 then 1 else 0 end) as is_red,
(case when sum(case when colorId in (11, 12, 13, 14) then 1 else 0 end)  > 0 then 1 else 0 end) as is_white,
(case when sum(case when colorId in (20, 21, 22, 23) then 1 else 0 end)  > 0 then 1 else 0 end) as is_yellow

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