Solved

recursive query

Posted on 2011-03-09
4
213 Views
Last Modified: 2012-05-11
How does one write a recursive query?  This would come into play where a table is self-referencing.   Like, a list of employees, where there is a primary Key and supervisor column, where the latter maps to the primary key.   So, If I want a list of employees everyone from person "X" on down, how do I do this?
0
Comment
Question by:HLRosenberger
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
4 Comments
 
LVL 32

Expert Comment

by:Ephraim Wangoya
ID: 35087033

You can use a recursive Common Table Expression (CTE) to do this kind of query
0
 
LVL 32

Accepted Solution

by:
Ephraim Wangoya earned 500 total points
ID: 35087074
here is an example

ID Parent
1  null
2  1
3  1
4  null
5  4
6  5

with CTE(ID, PARENT)
AS
(
      SELECT F.ID, F.PARENT
      FROM TABLE1 F
      WHERE PARENT IS NULL
      UNION ALL
      SELECT F.ID, F.PARENT
      FROM TABLE1 F
      INNER JOIN CTE FH ON FH.ID = F.PARENT
)

SELECT ID, PARENT FROM CTE
0
 
LVL 9

Expert Comment

by:gdupadhyay
ID: 35087209
I believe you are looking to make a tree for employee:
See example below:
ID: Emp ID
Name: Emp Name
Manager: Emp. Manager ID (NULL: Emp. have no manager)

ID      Name      Manager
1      a      NULL
2      b      1
3      c      1
4      X      2
5      Y      2
6      Z      1
7      P      3

WITH Employee_Tree (ID,
		Name,
		Manager,
		Depth) AS(
    SELECT  ID,
		Name,
		Manager,
		1 AS depth
     FROM Employee WITH (NOLOCK)
     WHERE MANAGER IS NULL
   UNION ALL
	SELECT  N.ID,
	        N.Name,
		N.Manager,
		ET.Depth + 1
		FROM Employee AS N WITH (NOLOCK)
	INNER JOIN Employee_Tree ET 
		ON ET.ID = N.Manager)
		SELECT ID,
		   Name,
		   Manager,
	FROM Employee_Tree

Open in new window

0
 
LVL 1

Author Closing Comment

by:HLRosenberger
ID: 35124508
Thanks!
0

Featured Post

Revamp Your Training Process

Drastically shorten your training time with WalkMe's advanced online training solution that Guides your trainees to action.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

For both online and offline retail, the cross-channel business is the most recent pattern in the B2C trade space.
In the first part of this tutorial we will cover the prerequisites for installing SQL Server vNext on Linux.
Using examples as well as descriptions, and references to Books Online, show the documentation available for date manipulation functions and by using a select few of these functions, show how date based data can be manipulated with these functions.
This videos aims to give the viewer a basic demonstration of how a user can query current session information by using the SYS_CONTEXT function

751 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question