sql : join and group by

Question

有3张 table :

movie(id, title, yr, score, votes, director) actor(id, name) casting(movieid, actorid, ord)

Q:Which were the busiest years for 'John Travolta'. Show the number of movies he made for each year.

答:我的尝试在语法上很旧。为什么 ？

select yr, count(*)
from 

(actor join casting
on (actor.id = casting.actorid)

join 
on (movie.id = casting.movieid)

group by yr 
having actor.name='John Travolta'

Answer 1

您缺少 join 之后的第二个表名

使用 where不是 having

尝试这个:

select yr, count(*)
from actor
join casting on actor.id = casting.actorid
join movie on movie.id = casting.movieid -- you were missing table name "movie"
where actor.name='John Travolta' -- "where", not "having"
group by yr 

还要注意我使用的一致格式。如果使用好的格式，更容易发现语法错误

仅供引用，having用于聚合函数，例如 having count(*) > 3