The average is null only if all values are null.
where exists (select from)
WHERE NOT EXISTS (SELECT XX FROM XXX)
和where in比较,
如果有intersect 还用exists,有71条结果,正确答案应该是1条结果
而且这边 括号内和括号外都是from movies
用where In 【亲切】; 要写where movie_id in ( )
四则运算结果显示的数字🔢
IN (2, 3, 4, 6)
BETWEEN XX AND XX (inclusive)
like not like
is null is not null
字母排序,空格在前,大写在前,小写在后
记得as ct括号里面要是双引号