结合两个select查询

Question

当我使用两个查询时，一个被初始调用，第二个在第一个结果循环中被调用。我想结合这两个查询，但迄今为止还没有办法。查询从拉的表是：

+--------------+ +--------------+ +--------------------------+ 
| table_1 | | table_2 | |   table_3   | 
+----+---------+ +----+---------+ +----+----------+----------+ 
| id | name | | id | name | | id | tbl1_id | tbl2_id | 
+----+---------+ +----+---------+ +----+----------+----------+ 
| 1 | tbl1_1 | | 1 | tbl2_1 | | id |  1 |  1 | 
| 2 | tbl1_2 | | 2 | tbl2_2 | | id |  3 |  2 | 
| 3 | tbl1_3 | | 3 | tbl2_3 | | id |  3 |  3 | 
| 4 | tbl1_4 | +----+---------+ +----+----------+----------+ 
+----+---------+ 

有一个许多人table_1和table_3table_2之间一对多的关系。到目前为止，我一直在使用分隔查询。一个查询返回table_1的所有内容，第二个查询返回连接到table_1到table_3的值table_2。但是，我想废除循环并减少发送到服务器的查询数量。我一直在使用一个JOIN尝试：

SELECT table_1.id, table_1.name, table_2.id, table_2.name 
FROM table_3 
LEFT JOIN table_1 ON (table_3.tbl1_id = table_1.id) 
LEFT JOIN table_1 ON (table_2.tbl2_id = table_2.id) 

这回非常希望，我想，除了它只有返回均table_3从table_1留下了一些值的值。我试过使用子查询：

SELECT table_1.id, 
    table_1.name, 
    (SELECT table_2.id FROM table_2, table_3 WHERE table_2.id = table_3.tbl2_id AND table_1.id = table_3.tbl1_id) AS tbl_2_id, 
    (SELECT table_2.name FROM table_2, table_3 WHERE table_2.id = table_3.tbl2_id AND table_1.id = table_3.tbl1_id) AS tbl_2_name 
FROM table_1 

这给了ERROR 1242。到目前为止，我还没有能够得到任何工作。我正在寻找的结果与此类似。

+---------------+---------------+---------------+---------------+ 
|table_1.id |table_1.name |table_2.id |table_2.name | 
+---------------+---------------+---------------+---------------+ 
|  1 | tbl1_1 |  1 | tbl2_1 | 
|  2 | tbl1_2 |  |  | 
|  3 | tbl1_3 |  2 | tbl2_2 | 
|  3 | tbl1_3 |  3 | tbl2_3 | 
|  4 | tbl1_4 |  |  | 
+---------------+---------------+---------------+---------------+ 

另外，我想可以订购两个table_1.name和table_2.name结果。如果有人有一个建议，请让我知道。

Answer 1

将LEFT JOIN更改为RIGHT JOIN，并且两个连接在查询中出现的顺序解决了此问题。这是工作代码的副本;

SELECT table_1.id, 
    table_1.name, 
    table_2.id, 
    table_2.name 
FROM table_3 
RIGHT JOIN table_2 ON (table_3.tbl2_id = table_2.id) 
RIGHT JOIN table_1 ON (table_3.tbl1_id = table_1.id) 
ORDER BY table_1.name ASC, table_2.name ASC; 

Answer 2

所以你只是试图打印出所有的相关配对？如何：

SELECT table_1.id, table_1.name, table_2.id, table_2.name 
FROM table_3 
INNER JOIN table_1 ON table_1.id = table_3.tbl1_id 
INNER JOIN table_2 ON table_2.id = table_3.tbl2_id 
ORDER BY table_1.id, table_2.id 

Answer 3

要想从TABLE_1有没有匹配的其它表，你应该使用一个外行JOIN而不是INNER JOIN的：

SELECT 
    table_1.id, 
    table_1.name, 
    table_2.id, 
    table_2.name 
FROM table_1 
LEFT JOIN table_3 ON table_3.tbl1_id = table_1.id 
LEFT JOIN table_2 ON table_3.tbl2_id = table_2.id 

结果：

 
table_1.id table_1.name table_2.id table_2.name 
1   'tbl1_1'  1   'tbl2_1'  
2   'tbl1_2'     ''   
3   'tbl1_3'  2   'tbl2_2'  
3   'tbl1_3'  3   'tbl2_3'  
4   'tbl1_4'     ''