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self join

Author

Topic

mr_dayal
Starting Member

37 Posts

Posted - 2008-08-21 : 10:06:51

I have a table category_master with following fileds

cat_id(pk), cat_name,cat_parent_id

This table is storing categories where one category may fall under some other category which is handled by cat_parent_id.
I want a self join so that tha data looks like this.

cat_id cat_name cat_parent_id cat_parent_name
1 Computers null null
2 scanners 1 Computers
3 printers 1 computers
4 harddisk 1 computers
5 internalhdd 4 harddisk
6 externalhdd 4 harddisk

so on..
What will be the query..

Mr Dayal

visakh16
Very Important crosS Applying yaK Herder

52326 Posts

Posted - 2008-08-21 : 10:10:43

Are you using sql 2005?

mr_dayal
Starting Member

37 Posts

Posted - 2008-08-21 : 10:13:00

yes, 2005 express Edition

Mr Dayal

visakh16
Very Important crosS Applying yaK Herder

52326 Posts

Posted - 2008-08-21 : 10:14:34

if sql 2005 use recursive cte approach like below

;
With Category_CTE (CatID,CatName,ParentID,ParentName)AS
(
SELECT cat_id, cat_name, cat_parent_id, cat_parent_name
FROM YourTable
WHERE cat_parent_id IS NULL
UNION ALL
SELECT c.CatID,c.CatName,c.ParentID,c.ParentName
FROM YourTable t
INNER JOIN Category_CTE c
ON c.CatID=t.cat_parent_id
)

SELECT * FROM Category_CTE

and if sql 2000 refer below link

http://support.microsoft.com/kb/248915

mr_dayal
Starting Member

37 Posts

Posted - 2008-08-21 : 10:23:58

It's not working ,I have Only three columns in my table

Mr Dayal

visakh16
Very Important crosS Applying yaK Herder

52326 Posts

Posted - 2008-08-21 : 10:26:52

modify like this

;
With Category_CTE (CatID,CatName,ParentID,ParentName)AS
(
SELECT cat_id, cat_name, NULL, NULL
FROM YourTable
WHERE cat_parent_id IS NULL
UNION ALL
SELECT t.cat_id,t.cat_name,c.CatID,c.CatName
FROM YourTable t
INNER JOIN Category_CTE c
ON c.CatID=t.cat_parent_id
)

SELECT * FROM Category_CTE

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