两张表
当我执行
select m.movieid,m.moviename,substr(m.moviename,-5,4) as years,avg(r.rate) as avgScore
FROM t_movie as m join t_rating as r on m.movieid = r.movieid
GROUP by m.movieid
HAVING avgScore >= 4;
报错:
Invalid column reference 'moviename'
改成下,就好了
select m.movieid,m.moviename,substr(m.moviename,-5,4) as years,avg(r.rate) as avgScore
FROM t_movie as m join t_rating as r on m.movieid = r.movieid
GROUP by m.movieid,m.moviename
HAVING avgScore >= 4;
我理解为,t_movie 表的 userid 与 moviename 两字段都是唯一的,所以分组的时候要一起写
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