Question

如果它们与第三个表的主键匹配，我正在尝试连接具有相同结构的两个表。然后我想根据第3个表中的列进行排序。

示例结构：

 Table 1 - id (VARCHAR) | title (VARCHAR) | expire (TIMESTAMP)

 Table 2 - id (VARCHAR) | title (VARCHAR) | expire (TIMESTAMP)

 Table 3 - id (VARCHAR) | views (VARCHAR) | expire (TIMESTAMP)

我认为这应该有效，但事实并非如此：

 SELECT * FROM table1 as t, table3 as t3 WHERE t.id = t3.id
 UNION
 SELECT * FROM table2 as t2, table3 as t3 WHERE t2.id = t3.id
 ORDER BY table3.expire DESC

有什么可以做到这一点？

Answer 1

使用JOIN将表3中的排序列放入，然后对其进行排序。

SELECT table_1.*, table_3.expire as t3_expire
  FROM table_1
  INNER JOIN table_3 on table_1.id = table_3.id
UNION ALL
SELECT table_2.*, table_3.expire
  FROM table_2
  INNER JOIN table_3 on table_2.id = table_3.id
ORDER BY t3_expire DESC;

Answer 2

一旦你有一个联盟，数据就无法区分了。所以你应该试试

 SELECT * FROM table1 as t, table3 as t3 WHERE t.id = t3.id
 UNION
 SELECT * FROM table2 as t2, table3 as t3 WHERE t2.id = t3.id
 ORDER BY expire DESC

这和你要问的一样好。除非你真的想到别的东西，否则你应该多分享一下。

Answer 3

你的意思是这样的吗？

SELECT 
    t.id AS t_id, t.title AS t_title, 
    t2.id AS t2_id, t2.title AS t2_title, 
    t3.expire 
FROM table3 AS t3
LEFT JOIN table1 as t ON t3.id = t.id
LEFT JOIN table2 as t2 ON t3.id = t2.id
ORDER BY t3.expire DESC

Answer 4

SELECT *
FROM Table3
  LEFT JOIN Table1 ON Table3.id = Table1.id
  LEFT JOIN Table2 ON Table3.id = Table2.id
WHERE
  Table1.id IS NOT NULL AND Table2.id IS NOT NULL
ORDER BY Table3.expire DESC

如果主键与第3个表匹配并按第3个表排序，我将如何连接2个表？

4 个答案: