Question

Table A :

id  members      
____________
1    a
2    b
3    c
4    c
4    d
5    e

Table B

id  countries
_____________
1   us
1   europe
1   australia
3   india
3   china
4   australia
4   canada
5   mexico

Result should look like

id   members   countries
___________________________
1     a        us
1              europe
1              australia
2     b
3     c        india
3              china
4     c        australia
4     d        cananda
5     e         mexico

I am sorry if I am editing at wrong place.

@Martin Thanks for your reply. It works great for 2 tables. But actually I am trying to combine more than 2. Let’s say I have another table C

id     prime_members
---------------------
1       p1
1       p2

I need the result to look like

id   members   countries     prime_mem
___________________________________________
1     a        us            p1
1              europe        p2
1              australia
2     b
3     c        india
3              china
4     c        australia
4     d        cananda
5     e         mexico

so I tried the query like this

 ;WITH A AS 
( SELECT id, members,
 ROW_NUMBER() OVER (PARTITION BY id ORDER BY members) AS RN FROM @A ),
  B AS 
  ( SELECT id, countries, 
  ROW_NUMBER() OVER (PARTITION BY id ORDER BY countries) AS RN FROM @B ),
   C AS 
  ( SELECT id,PRIME_MEM,
  ROW_NUMBER() OVER (PARTITION BY id ORDER BY PRIME_MEM) AS RN FROM @C )

   SELECT COALESCE(A.id,B.id,C.ID) AS id,  A.members, B.countries,C.PRIME_MEM
    FROM A FULL OUTER JOIN B on A.id = B.id AND A.RN=B.RN
    FULL OUTER JOIN C  ON A.ID =C.ID AND C.RN = A.RN 

---

then I got result like this:

id   members   countries     prime_mem
___________________________________________
1     a        us            p1
1              europe        
1              australia
1                            p2
2     b
3     c        india
3              china
4     c        australia
4     d        cananda
5              mexico

I figured it out that C.RN=B.RN gives correct output because A.RN does not have RN>1 as it has only 1 row. Here it is easy because only 3 tables and few rows. But in real time how to figure out and solve this problem. Also Table A is a reference table, i.e. values for ID in table B and C will be present in table A.

Any help is appreciated.
Thanks.

Answer 1

There is no “natural order” to tables so (unless there is an additional column such as id that you haven’t shown us) there is nothing that can be used to ensure that the order you have in your example source data will be preserved in the final output.

;WITH A AS
(
SELECT id,
       members, 
       ROW_NUMBER() OVER (PARTITION BY id ORDER BY members) AS RN
FROM tableA
),
B AS
(
SELECT id,
       countries, 
       ROW_NUMBER() OVER (PARTITION BY id ORDER BY countries) AS RN
FROM tableB
)
SELECT COALESCE(A.id,B.id) AS id, 
       A.members,
       B.countries
FROM A FULL OUTER JOIN B on A.id = B.id AND A.RN=B.RN

Returns (Note china and india have swapped places as my answer orders alphabetically within each group)

id          members countries
----------- ------- ---------
1           a       australia
1           NULL    europe
1           NULL    us
2           b       NULL
3           c       china
3           NULL    india
4           c       australia
4           d       canada
5           NULL    mexico