Question

我需要写一个查询，我甚至不知道从哪一个开始。我有一组我没有创建并且无法更改的表。

member table
+----+-------+
| id | class |
+----+-------+
|  1 |     1 |
|  2 |     2 |
+----+-------+

member_data table
+----+------------+-----------+
| id | first_name | last_name |
+----+------------+-----------+
|  1 |       John |     Jones |
|  2 |       Juan |     Jones |
+----+------------+-----------+

member_entries table
+----+-----------+-------+------------+
| id | member_id | title |    date    |
+----+-----------+-------+------------+
|  1 |         1 | test1 | 1265042580 |
|  2 |         1 | test2 | 1265042581 |
|  3 |         2 | test3 | 1265042582 |
|  4 |         3 | test4 | 1265042583 |
+----+-----------+-------+------------+

我需要从member_data中选择id，first_name，从member_entries中选择最新的标题，以及与member_id匹配的member_entries的总数。我需要能够在第一个表中选择成员的类是特定数字的位置。我还需要能够通过任何这些列进行排序。如果我选择了成员类为1的成员，那么这就是我需要输出的内容。

+----+------------+-------+------------+
| id | first_name | title |    date    |
+----+------------+-------+------------+
|  1 |       John | test2 | 1265042581 |
+----+------------+-------+------------+

Answer 1

SELECT member.id, member_data.first_name, member_entries.title, member_entries.date
FROM member
INNER JOIN member_data ON member.id = member_data.member_id
INNER JOIN member_entries ON member.id = member_entries.member_id
WHERE member.class = 1
ORDER BY member_entries.date DESC
LIMIT 1

并根据需要构建WHERE和ORDER BY子句。

Answer 2

 SELECT m.id, md.first_name, me.title, me.date
 FROM member m 
 INNER JOIN member_data md ON md.id = m.id 
 INNER JOIN member_entries me on me.id = m.id
 WHERE me.date =
   (SELECT MAX(date) FROM member_entries WHERE id = m.id)
 AND m.class = 1

mysql查询帮助 - 按场景复杂的连接/顺序

2 个答案: