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涉及三个表格订购数据的问题
原标题:Trouble writing MySQL query involving ordered data from three tables
  • 时间:2011-03-25 03:08:25
  •  标签:
  • mysql
  • sql

我的表格称为tags

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

之后的表格称为coupon_tags

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

最后,一个称为<代码>coupons的表格在这里是相关部分(与其他地方的政变一样):

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

我需要写一个问题: 我想通过第二张表格中最常用的10个顶级标的顺序表上的第一个表格获得标号,但只看政变。 符合其他标准——“区”为某一区。 最终,只有来自某个地区的10个顶顶端。 我从未做过一个三轮问答,任何帮助?

我试图保持这一纯粹的结构,因为我有一个部分可行的购买力平价解决办法,但这种解决办法是令人费解和非常缓慢的。

最佳回答
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 
问题回答

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