Solved

Sample Clause  After Filtering With A WHERE Clause with Table Joins

Posted on 2008-10-20
7
330 Views
Last Modified: 2013-12-18
Hello -

Im attempting to pull a 5% sample from the resulting dataset of a table join.  However, when trying to run this code I get an error.  I believe its because the sample clause is getting confused as to which table to sample.  Is there a way to get around this? What is the smartest way to get around this limitation of the Sample Clause?

Sample code below.

Thanks in advance.
SELECT a.Contact a.ContactNum b.Address c.Phone
FROM a.ExecInfo, b.Location, c.Demographics
SAMPLE(5)
WHERE a.LinkID = b.LinkID
   AND b.LinkID = c.LINKID;

Open in new window

0
Comment
Question by:Keenetic
[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
  • 2
7 Comments
 
LVL 29

Accepted Solution

by:
MikeOM_DBA earned 125 total points
ID: 22759646

Try this:

WITH Q0 AS (
SELECT a.Contact a.ContactNum b.Address c.Phone
FROM a.ExecInfo, b.Location, c.Demographics
WHERE a.LinkID = b.LinkID
   AND b.LinkID = c.LINKID)
SELECT * FROM Q0 SAMPLE(5);

Open in new window

0
 
LVL 29

Expert Comment

by:MikeOM_DBA
ID: 22759746

-- Or --
 Maybe you need to sample the largest table only:

WITH Q0 AS (
SELECT Contact, ContactNum, LinkID
  FROM ExecInfo SAMPLE(5))
SELECT a.Contact, a.ContactNum, b.Address c.Phone
  FROM Q0 a, b.Location, c.Demographics
 WHERE a.LinkID = b.LinkID
   AND b.LinkID = c.LINKID);

Open in new window

0
 

Expert Comment

by:dxladner
ID: 22760302
The SAMPLE clause in ORACLE is basically:
SAMPLE(the number that you want )

The are some limitations to this clause: 1. Discrepancies in actual percentage in the returned data2. Using views and certain joins.  
0
 
LVL 4

Expert Comment

by:hqassap
ID: 22764949
Try this:

SELECT *
  FROM (SELECT a.contact, a.contactnum, b.address, c.phone
          FROM a.execinfo, b.LOCATION, c.demographics
         WHERE a.linkid = b.linkid AND b.linkid = c.linkid)
 WHERE ROWNUM < 6

Open in new window

0
 

Expert Comment

by:dxladner
ID: 22767013
The RowNum clause will get you the first 6 rows of data only. If that is all you are looking for  then use hgassap's example. But using the RowNum will not pull RANDOM sampling throughout the database. You must use the SAMPLE keyword.
0

Featured Post

Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

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

Introduction A previously published article on Experts Exchange ("Joins in Oracle", http://www.experts-exchange.com/Database/Oracle/A_8249-Joins-in-Oracle.html) makes a statement about "Oracle proprietary" joins and mixes the join syntax with gen…
Using SQL Scripts we can save all the SQL queries as files that we use very frequently on our database later point of time. This is one of the feature present under SQL Workshop in Oracle Application Express.
This video shows how to set up a shell script to accept a positional parameter when called, pass that to a SQL script, accept the output from the statement back and then manipulate it in the Shell.
This video shows how to recover a database from a user managed backup
Suggested Courses

634 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