SELECT title,COUNT(actorid)
FROM movie JOIN casting ON movieid=movie.id
WHERE yr = 1978
GROUP BY id,title
ORDER BY COUNT(actorid) DESC,title
这两个运行结果一致,那么GROUP BY/ORDER BY 后面加了逗号分隔开表示的是什么意思?逗号分隔有什么意义?
SELECT title,COUNT(actorid)
FROM movie JOIN casting ON movieid=movie.id
WHERE yr = 1978
GROUP BY title
ORDER BY COUNT(actorid) DESC
隔开是多个字段参与分组和排序
多个字段分组排序规则:
当第一个字段相同时,参考第二个字段,。。。。
可以理解为对字符串排序规则一样。
GROUP BY id,title先对id分组,id相同的再按title分组。