将多个表合并为一个ID

Question

我有许多具有以下格式的表：

表格1

[idA] [numA]
 NULL   8
 1      10
 2      15
 3      16

表2

[idB] [numB]
 2      14
 3      30
 4      32

表3

[idC] [numC]
 NULL   56
 1      24
 4      37
 5      36

...

现在，我不确定如何制定T-Sql查询以产生以下结果：

[id] [numA] [numB] [numC] ...
NULL  8      0      56
1     10     0      24
2     15     14     0
3     16     30     0
4     0      32     37
5     0      0      36

关于如何解决这个问题有什么建议吗？

Answer 1

我提供了具有完全外部联接的解决方案，因为这似乎是自然的方法：

SELECT coalesce(a.id, b.id, c.id, . . .) as id,
       a.NumA, b.NumB, c.NumC, . . .
FROM TableA a full outer join
     TableB b
     on a.id = b.id full outer join
     TableC c
     on coalesce(a.id, b.id) = c.id

但是，需要仔细编写查询，以使合并保持一致。 这种方法的一个优点是，它应该在查询的id列上使用索引。

Answer 2

请尝试这个

select id, max(numa),max(numb),max(numc) from
(
select id,numa,0 as numb,0 as numc from tb1
union all
select id,0 as numa,numb as numb,0 as numc from tb2
union all
select id,0 as numa,0 as numb,numc as numc from tb3
)X
group by id
order by id

感谢Rajath

Answer 3

SELECT Maintable.id, 
       Table1.numA, 
       Table2.numB, 
       Table3.numC 
FROM   (SELECT ida AS id 
        FROM   Table1 
        UNION 
        SELECT idb AS id 
        FROM   Table2 
        UNION 
        SELECT idc AS id 
        FROM   Table3) MainTable 
       LEFT JOIN Table1 
         ON Maintable.id = Table1.Ida 
       LEFT JOIN Table2 
         ON Maintable.id = Table2.idB 
       LEFT JOIN Table3 
         ON Maintable.id = Table3.idC