Question

我需要帮助来连接三个表。我可以以某种方式联接两个表table1和table2以获得所需的输出，但是我想联接另一个表以获取一些新的相关列。这是我的查询：

select 
[from_bus] as [Node], 
[from_bus_id]  as [Node_id]
from table1 
union 
select 
[to_bus] as [Node], 
[to_bus_id]  as [Node_id]
from table1
union
select 
[from_bus] as [Node], 
[from_bus_id]  as [Node_id]
from table2
union 
select 
[to_bus] as [Node], 
[to_bus_id]  as [Node_id]
from table2

查询表1和表2的输出：

Node Node_ID
A_22  1
A_11  2
B_33  3
C_25  4

Node和Node_ID是唯一的。现在，我有了另一个table3，我需要从中另一个列(Zone_ref)包含相应的IDs的{{1}}。

Zone

我想要类似的东西

    table3: 
    Zone   Node_Name  Zone_ref
    A      A_22        1
    A      A_11        1
    B      B_33        3 
    B      B_44        3     
    C      C_31        4
    C      C_25        4

有一些公共字段可以连接表，但不知道如何将两个表中的一个查询与第三个表集成在一起。需要您的建议。顺便说一句，我正在使用访问数据库。谢谢。

Answer 1

尝试使用Join嵌套子查询。如下所示：

select a.Node, a.Node_id, b.Zone_ref from (
 select 
 [from_bus] as [Node], 
 [from_bus_id]  as [Node_id]
 from table1 
 union 
 select 
 [to_bus] as [Node], 
 [to_bus_id]  as [Node_id]
 from table1
 union
 select 
 [from_bus] as [Node], 
 [from_bus_id]  as [Node_id]
 from table2
 union 
 select 
 [to_bus] as [Node], 
 [to_bus_id]  as [Node_id]
 from table2 ) a
INNER JOIN table3 b ON a.Node = b.Node_Name

将两个表的查询与另一个表联接

1 个答案: