SQL从1 x N中选择所有大于

Question

我有桌子books，bookType它们构成1 X n关系。

books

+-----+------------------+----------+-------+
| id  |      title       | bookType | price |
+-----+------------------+----------+-------+
|   1 | Wizard of Oz     |        3 |    14 |
|   2 | Huckleberry Finn |        1 |    16 |
|   3 | Harry Potter     |        2 |    25 |
|   4 | Moby Dick        |        2 |    11 |
+-----+------------------+----------+-------+

bookTypes

+-----+----------+
| id  |   name   |
+-----+----------+
|   1 | Fiction  |
|   2 | Drama    |
|   3 | Children |
+-----+----------+

如果所有书籍的价格都比12（$）高，我该如何检索bookTypes？在这种情况下，预期输出为：

+-----+----------+
| id  |   name   |
+-----+----------+
|   1 | Fiction  |
|   3 | Children |
+-----+----------+

Answer 1

您可以使用not exists：

select t.*
from bookTypes t
where not exists (
    select 1
    from books b
    where b.bookType = t.id and b.price < 12
)

如果要选择至少具有一本关联书的书类型：

select t.*
from bookTypes t
where 
    exists (select 1 from books b where b.bookType = t.id)
    and not exists (select 1 from books b where b.bookType = t.id and b.price < 12)