mysql - 为什么此 SQL 给出列无法解析错误？

Question

我正在尝试运行一个非常简单的 CASE...WHEN 语句:

SELECT userid, sum(end_time-start_time)/60 AS timespent_minutes, 
                    CASE WHEN webid = '324234' THEN 'CA'
                    ELSE 'Other' END AS storeloc
FROM time_spent_intervals
WHERE (ds = '2018-12-01')
GROUP BY userid, storeloc

但我收到以下错误:

Error: SYNTAX_ERROR
line 6:38: Column 'storeloc' cannot be resolved

Answer 1

尝试在 GROUP BY 中重复表达式:

SELECT userid, sum(end_time-start_time)/60 AS timespent_minutes, 
       (CASE WHEN webid = '324234' THEN 'CA' ELSE 'Other' END) AS storeloc
FROM time_spent_intervals
WHERE ds = '2018-12-01'
GROUP BY userid, (CASE WHEN webid = '324234' THEN 'CA' ELSE 'Other' END) ;

尽管 MySQL 允许为 GROUP BY 使用列别名，但并非所有数据库都这样做。我猜您并没有真正使用 MySQL。