CODEWITHSUNDEEP
sql-serversql-server-2008recursive-query
darthun08
darthun08

Reputation: 95

How to show recursive parentID in a single column in SQL

Here is the example structure of the table:

ID    Name     ParentID
-----------------------
1     Ancestor      NULL
2     GrandFather   1
3     GrandMother   1
4     Child         3

I'm trying to write a query that would return 

ID     Name        Family
----------------------------
 1     Ancestor 
 2     GrandFather Ancestor
 3     GrandMother Ancestor
 4     Child       Ancestor^GrandMother

The tricky part is that I want to show the family of all rows and in a top-down order.

If anyone can point me in the right direction, it would be appreciated :)

EDIT :: This is the real query, but it follows the same idea. it returns an error on line : marketparent.family + '^'+ t2.marketGroupName because it cant find marketparent

WITH marketparent ( marketGroupID,parentGroupID, marketGroupName,family)
AS
(
SELECT marketGroupID,
       parentGroupID,
       marketGroupName,
       '' as family 
 FROM EVE.dbo.invMarketGroups
 WHERE parentGroupID IS NULL
UNION ALL

    SELECT t2.parentGroupID,
     t2.marketGroupID,
     t2.marketGroupName,
     marketparent.family + '^'+ t2.marketGroupName
     FROM EVE.dbo.invMarketGroups as t2
     INNER JOIN marketparent as mp
     ON mp.marketGroupID = t2.parentGroupID
)

-- Statement using the CTE

SELECT TOP 10 *
FROM marketparent;

Upvotes: 8

Views: 11140

Answers (3)

Diego
Diego

Reputation: 36146

select T.ID, T.Name, (select name from table where ID=T.ParentID)as Family
from table T

Upvotes: 0

Mikael Eriksson
Mikael Eriksson

Reputation: 138960

You can use a recursive Common Table Expression.

declare @T table
(
  ID int,
  Name nvarchar(15),
  ParentID int
);

insert into @T values
(1,     N'Ancestor',      NULL),
(2,     N'GrandFather',   1),
(3,     N'GrandMother',   1),
(4,     N'Child',         3);

with C as
(
  select T.ID,
         T.Name,
         T.ParentID,
         cast(N' ' as nvarchar(max)) as Family
  from @T as T
  where T.ParentID is null
  union all
  select T.ID,
         T.Name,
         T.ParentID,
         C.Family+'^'+C.Name
  from @T as T
    inner join C
      on T.ParentID = C.ID
)
select C.ID,
       C.Name,
       stuff(C.Family, 1, 2, '') as Family
from C;

Upvotes: 1

user330315
user330315

Reputation:

You did not specify your DBMS, so I'm assuming PostgreSQL

WITH RECURSIVE fam_tree (id, name, parent, family) as 
(
  SELECT id, 
         name, 
         parentid, 
         ''::text as family
  FROM the_unknown_table
  WHERE parent IS NULL

  UNION ALL

  SELECT t2.id, 
         t2.name, 
         t2.parentid, 
         fam_tree.family || '^' || t2.name
  FROM the_unknown_table t2 
     INNER JOIN fam_tree ON fam_tree.id = t2.parentid
)
SELECT *
FROM fam_tree;

This is standard SQL (except for the ::text typecast) that should work with very few changes on most modern DBMS.

Edit:

For SQL Server you would need to replace the standard concatention character with Microsoft's non-standar + (and you need to remove the recursive keyword which is required by the standard but for some strange reason rejected by SQL Server)

WITH fam_tree (id, name, parent, family) as 
(
  SELECT id, 
         name, 
         parentid, 
         '' as family
  FROM the_unknown_table
  WHERE parent IS NULL

  UNION ALL

  SELECT t2.id, 
         t2.name, 
         t2.parentid, 
         fam_tree.family + '^' + t2.name
  FROM the_unknown_table t2 
     INNER JOIN fam_tree ON fam_tree.id = t2.parentid
)
SELECT *
FROM fam_tree;

Upvotes: 10

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