Question

我很好奇是否可以加入两个表来重温下面的内容。

**superTable**

id | project 
1     aaa         
2     bbb    

**approvedTable**
id | statusStep | Emp
1     BossMan    Gregor
1     FirstMate  Hans

**notApprovedTable**
id | statusStep | Emp
1      Sailor     Julia
1      Sr.Sailor  Dave

我希望将两个表'approvedTable'和'notApprovedTable'加入id上的superTable，以便有类似的内容

   id | project | approvedStep |   Emp    | notApprovedStep | Emp
   1     aaa       BossMan        Gregor        null          null
   1     aaa       FirstMate      Hans          null          null
   1     aaa       null           null          Sailor        Julia    
   1     aaa       null           null          Sr.Sailor     Dave

如果我做一个简单的连接，就会创建类似这样的东西

   id | project | approvedStep |   Emp    | notApprovedStep | Emp
   1     aaa       BossMan        Gregor        Sailor        Julia
   1     aaa       FirstMate      Hans          Sailor        Julia 
   1     aaa       BossMan        Gregor        Sr.Sailor     Dave
   1     aaa       FirstMate      Hans          Sr.Sailor     Dave

Answer 1

UNION可以帮助你

SELECT s.ID,s.project,a.statusStep approvedStep,a.Emp,NULL AS notApprovedStep, NULL AS notApprovedEmp
FROM  superTable s
INNER JOIN approvedTable a ON s.ID=a.ID 
UNION 
SELECT s.ID,s.project,NULL AS approvedStep,NULL AS Emp,na.statusStep AS notApprovedStep,na.Emp AS notApprovedEmp
FROM  superTable s
INNER JOIN notApprovedTable na ON s.ID=na.ID

Answer 2

两个查询结果与UNION ALL粘合：

select s.id, s.project, 
       a.statusstep as approved_step, a.emp as approved_emp, 
       null as not_approved_step, null as not_approved_emp
from supertable s
join approvedtable a on a.id = s.id
union all
select s.id, s.project, 
       null as approved_step, null as approved_emp, 
       na.statusstep as not_approved_step, na.emp as not_approved_emp
from supertable s
join notapprovedtable na on na.id = s.id

SQL Server - 两个连接到同一列上的同一个表

2 个答案: