MySQL 计数（CASE WHEN ... THEN DISTINCT 列）
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时间：2020-08-31 20:32:34 来源:igfitidea点击:
MySQL COUNT(CASE WHEN ... THEN DISTINCT Column)
提问by GGio
My query:
我的查询：
COUNT(
CASE WHEN YEAR(FieldValue) = YEAR(CURDATE())
AND MONTH(FieldValue) = MONTH(CURDATE())
THEN 1
END
) AS mtd
I want something like:
我想要这样的东西：
COUNT(
CASE WHEN YEAR(FieldValue) = YEAR(CURDATE())
AND MONTH(FieldValue) = MONTH(CURDATE())
THEN DISTINCT ColumnID
END
) AS mtd
This gives an error. I can not use GROUP BY. If I add DISTINCT before CASE it does not work either it treats FieldValue column as DISTINCT but I want it to count ColumnID as distinct.
这给出了一个错误。我不能使用GROUP BY。如果我在 CASE 之前添加 DISTINCT 它不起作用，或者它将 FieldValue 列视为 DISTINCT 但我希望它将 ColumnID 计数为不同的。
Please help
请帮忙
回答by echo_Me
Try this
尝试这个
COUNT(DISTINCT(
CASE WHEN YEAR(FieldValue) = YEAR(CURDATE())
AND MONTH(FieldValue) = MONTH(CURDATE())
THEN ColumnID
END )
) AS mtd
