无法编写涉及来自三个表的有序数据的MySQL查询

Question

I have a table called tags , like this:

+-------+----------+
| tagID | tagName  |
+-------+----------+
|     1 | jewelery |
|     2 | gifts    |
|     3 | asdf     |
|     4 | fashion  |
|     5 | diamonds |
+-------+----------+

Then a table called coupon_tags , like this:

+-------+----------+
| tagID | couponID |
+-------+----------+
|     1 |        1 |
|     2 |        1 |
|     3 |        2 |
|     4 |        2 |
|     5 |        3 |
+-------+----------+

And lastly, a table called coupons , here are the pertinent parts (id is the same as couponID elsewhere):

+----+-----------------+
| id | zone            |
+----+-----------------+
|  1 | Los Angeles     |
|  2 | Orange County   |
|  3 | Los Angeles     |
|  5 | Orange County   |
|  6 | Orange County   |
+----+-----------------+

What I need to write a query for: I want to get tagNames via the first table that correspond to the ordered list of the top 10 most used tagIDs in the second table, but it only looks through couponIDs that match another criteria - that the "zone" be a certain zone. In the end, only the top 10 tagNames from a certain zone will show. I've never done a triple-table query before, any help?

I'm trying to keep this purely SQL, as I had a partially working PHP solution but it was messy and very slow.

Answer 1

SELECT tags.tagName FROM
(SELECT tagID, COUNT(*) FROM
 coupon_tags 
 JOIN coupons ON coupons.couponID = coupon_tags.couponID AND zone = 'Los Angeles' 
 GROUP BY tagID ORDER BY COUNT(*) DESC LIMIT 10) AS most_used
JOIN tags ON most_used.tagID = tags.tagID