多表连接查询

Question

我有一个主表为“master_tbl”，它具有以下字段：

m_id(PK) 
m_name 

两个从表可以是：

Slave-1 : 
--------- 
sl1_id PK 
sl1_name 
sl_m_id FK 

Slave-2 : 
--------- 
sl2_id PK 
sl2_name 
sl2_m_id FK 

我需要输出为像一个查询匹配记录的详细信息应显示如下：

m_id  m_name sl1_name(or sl2_name) 

最后显示字段d取slave1或Slave2表中匹配记录的名称。

Answer 1

SELECT m_id, m_name, sl1_name as `sl1_name(or sl2_name)` FROM slave_1 S1 
     INNER JOIN master_tbl M ON S1.sl1_m_id = M.m_id 
UNION 
SELECT m_id, m_name, sl2_name as `sl1_name(or sl2_name)` FROM slave_2 S2 
     INNER JOIN master_tbl M ON S2.sl2_m_id = M.m_id 

Answer 2

内部联接查询中使用

SELECT mt.name, s1.sl1_name, s2.sl2_name FROM master_tbl as mt 
INNER JOIN Slave-1 as s1 ON s1.sl_m_id = mt.m_id 
INNER JOIN Slave-2 as s2 ON s2.sl2_m_id = mt.m_id