您可以使用CASE WHEN别名来分组吗？

问题描述

限时删除！！

我有一个SELECT语句是从CASE WHEN THEN状态（或可以使用多个IF语句）中计算出来的，它被定义为'Length'，并且我需要将结果正确地分组在一起。 SELECT似乎正在工作，但该组将它们分组错了。这是我的声明：

pre $

您需要在中列名的单引号， code>子句。

I have a SELECT statement being calculated from a CASE WHEN THEN state (or could use multiple IF statements) aliased as 'Length', and I need to correctly GROUP the results together. The SELECT seems to be working, but the group groups them wrong. Here is my statement:

SELECT CASE
    WHEN DATEDIFF(o.EndDate, o.StartDate) < 30 THEN '<1 Month'
    WHEN DATEDIFF(o.EndDate, o.StartDate) < 90 THEN '1 - 2 Months'
    WHEN DATEDIFF(o.EndDate, o.StartDate) < 210 THEN '3 - 4 Months'
    ELSE '>4 Months' END AS 'Length',
    COUNT(DISTINCT(person.ID)) AS 'COUNT'
FROM person
    INNER JOIN opportunity AS o
    INNER JOIN Organization AS org
    ON person.EntityID = o.id
        AND O.OrganizationID = Org.ID
WHERE person.TitleID = 2
    AND o.bID = 1
GROUP BY 'Length'
ORDER BY 'Length' ASC;

This groups all results into '3 - 4 Months' which isn't right..

解决方案

You need to use the whole CASE statement in the GROUP BY clause if you don't wrapped it in a subquery.

SELECT  CASE
            WHEN DATEDIFF(o.EndDate, o.StartDate) < 30 THEN '<1 Month'
            WHEN DATEDIFF(o.EndDate, o.StartDate) < 90 THEN '1 - 2 Months'
            WHEN DATEDIFF(o.EndDate, o.StartDate) < 210 THEN '3 - 4 Months'
            ELSE '>4 Months'
        END AS `Length`,
        COUNT(DISTINCT(person.ID)) AS `COUNT`
FROM    person
        INNER JOIN opportunity AS o
            ON person.EntityID = o.id
        INNER JOIN Organization AS org
            ON o.OrganizationID = Org.ID
WHERE   person.TitleID = 2
        AND o.bID = 1
GROUP   BY  CASE
                WHEN DATEDIFF(o.EndDate, o.StartDate) < 30 THEN '<1 Month'
                WHEN DATEDIFF(o.EndDate, o.StartDate) < 90 THEN '1 - 2 Months'
                WHEN DATEDIFF(o.EndDate, o.StartDate) < 210 THEN '3 - 4 Months'
                ELSE '>4 Months'
            END
ORDER   BY Length ASC;

Remove also the single quotes around the column name in the ORDER BY clause.

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