您可以在CASE WHEN THEN别名下进行GROUP BY吗？

您可以在CASE WHEN THEN别名下进行GROUP BY吗？

如果您没有将整个

CASE

语句

GROUP BY

包装在子查询中，则需要使用该语句中的整个语句。

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.IDWHERe   person.TitleID = 2        AND o.bID = 1GROUP   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'  ENDORDER   BY Length ASC;

还要删除

ORDER BY

子句中列名周围的单引号。