SQL select from 1 x N where all bigger than - mysql

Question

I have tables books and bookType which pose a 1 X n relationship.
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 |
+-----+----------+
How would I retrieve bookTypes where all books are more expensive than e.g. 12($)?
In this case, the expected output would be:
+-----+----------+
| id | name |
+-----+----------+
| 1 | Fiction |
| 3 | Children |
+-----+----------+

Answer 1

You can use not exists:
select t.*
from bookTypes t
where not exists (
select 1
from books b
where b.bookType = t.id and b.price < 12
)
If you want to select book types that also have at least one associated book:
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)

Answer 2

Do a GROUP BY, use HAVING to return only booktypes having the lowest price > 12.
SELECT bt.name
FROM bookTypes bt
INNER JOIN books b ON b.bookType = bt.id
group by bt.name
HAVING SUM(b.price <= 12) = 0;

Answer 3

You can directly consider using having min(price) >= 12 with grouping by bookType
select t.id, t.name
from bookTypes t
join books b
on t.id = b.bookType
group by b.bookType
having min(price) >= 12
Moreover, if your DB's version is at least 10.2, then you can also use some window functions for analytical queries such as min(..) over (partition by .. order by ..) :
with t as
(
select t.id, t.name, min(price) over (partition by bookType) as price
from bookTypes t
join books b
on t.id = b.bookType
)
select id, name
from t
where price >= 12
in which min() over (..) window function determines minimum price for each booktype by use of partition by bookType
Demo

Answer 4

I think GMB's solution is likely the best so far. But for sake of completeness: You can also use the ALL operator with a correlated subquery. That's probably the most straight forward solution.
SELECT *
FROM booktypes bt
WHERE 12 < ALL (SELECT b.price
FROM books b
WHERE b.booktype = bt.id);

Answer 5

Can you not just select from books inner join bookTypes on id WHERE price > 12?
SELECT bt.*
FROM bookTypes bt
INNER JOIN books b ON b.bookType = bt.id
WHERE b.price > 12