Question

我有两张表如下：

    Parent                          Child   
ABID    DEPARTMENT TIME         ABID    ABDEPARTMENT 
1       SC          10          1       MC           
1       -ALL-       15          2       SY           
1       MC          20                     
2       SC          20                             
2       -ALL-       15                             
2       MC          20

我想写一个连接查询，以便输出查询

应该具有匹配的ABID和部门。
如果父表中没有匹配的部门，则查询应该使用DEPARTMENT'-ALL - '

所以输出应该是

ABID    DEPARTMENT TIME  ABID   ABDEPARTMENT
1          MC        20   1       MC
2        -ALL-       15   2       SY

UPDATE1：

我目前的查询是：

select * from Child LEFT join Parent on Child.AbId = Parent.AbId and Child.ABDEPARTMENT= Parent.DEPARTMENT

提供以下输出：

ABID    DEPARTMENT ABID ABDEPARTMENT TIME     
1          MC      1          MC      20
2          SY      NULL      NULL     NULL

Answer 1

可能的解决方案：

select *
  from parent p
  join child c on p.abid = c.abid and c.abdepartment = p.department
 union
select *
  from parent p
  join child c on p.abid = c.abid and p.department = '-ALL-'
 where not exists (select null
                     from parent p
                    where p.abid = c.abid
                      and c.abdepartment = p.department)

Oracle：使用ON子句中的条件连接表

1 个答案: