两个表之间的SQL查询

Question

我只是想创建一个查询，但不能成功创建它。 我只想从两个表中获取数据，但没有创建正确的查询。 这是我的问题。

this is my first table emp with id as a primary key 
id(primary key)  name 
101     A 
102     B 
103     C 
104     D 

this is my second table boss with bossid as a foreign key with emp table column id 
bossid(foreign key with emp table in column id)   empid 
102              101 
103              104 




now i just want to create a sql query which return me a data like this 
bossid name empid name 
102  B  101  A 
103  C  104  D 


In this return query 'B' and 'C' is boss name from emp table with bossid '102','103' and 'A' and 'D' is the emp name from same table emp with empid '101','104' join with bossid from bossname table and id with empname table. 

在此先感谢。

Answer 1

您可以使用LEFT JOIN或加入

SELECT  A.bossid as bossid, B.name as name, A.empid as empid, C.name as name 
FROM  boss A 
LEFT JOIN emp B 
    ON   A.bossid = B.id 
LEFT JOIN emp C 
    ON  A.empid = C.id 

Answer 2

看到查询：

SELECT 
    bossid, emp.name, empid, emp2.name 
from boss 
JOIN emp ON emp.Id = boss.bossid 
join emp emp2 ON emp2.Id = boss.empid