mysql - 如何正确执行查询？

Question

STRUCTURE TABLES AND ERROR WHEN EXECUTE QUERY ON SQLFIDDLE

查询:

SELECT 
            n.Type as Type,
            n.UserIdn as UserIdn,
            u.Username as Username,
            n.NewsIdn as NewsIdn,
            n.Header as Header,
            n.Text as Text,
            n.Tags as Tags,
            n.ImageLink as ImageLink,
            n.VideoLink as VideoLink,
            n.DateCreate as DateCreate,
            SUM(l.Type = 'up') as Uplikes, 
            SUM(l.Type = 'down') as Downlikes,
            (SUM(l.Type = 'up') - SUM(l.Type = 'down')) as SumLikes
        FROM News n 
            INNER JOIN Users u ON n.UserIdn = u.UserIdn 
            LEFT JOIN Likes l ON n.NewsIdn = l.NewsIdn
            WHERE SumLikes > 20 AND n.DateCreate < STR_TO_DATE('2014-01-03 14:17:43', '%Y-%m-%d %H:%i:%s')
        GROUP BY n.id
        ORDER by SumLikes DESC

当我使用查询时出现错误:

Unknown column 'SumLikes' in 'where clause'...

我知道“SumLikes”中存在错误，但如何正确地进行 sql 查询？

请告诉我如何制作？

Answer 1

为列添加别名时，我们需要对其进行不同的处理。

删除 SumLikes > 20 并在 GROUP BY

之后添加一个额外的命令

示例:

HAVING SumLikes > 20