Q
Problem solve Get help with specific problems with your technologies, process and projects.

Removing repeated values in a table

What is the most efficient way of removing repeated values in a table? Currently the script I am using only removes...

duplicates, so it must be run multiple times if the records are triplicated, etc.

Let's say for example that table T has a column C that repeats several times. You want to remove the repeated values.

1) Create a temporary view.

    create view V
        as select count(*) as CNT , C
           from T
           group by C
           having count(*) > 1;
2) Create a temporary table.
    create TABLE T2 as SELECT * from T
3) Try this PL/SQL block.
    declare cursor c_v is select C from V;

     FOR cv in c_v LOOP
          Insert into T2 SELECT * FROM T where T.C = cv.C and ROWNUM = 1;
     END LOOP;
4) DELETE ALL repeated.
     DELETE FROM T  where C in (select C from V)
5) Add only one repeated row.
    insert into T select * from T2;
6) Drop TABLE T2;

7) Drop VIEW V;

For More Information

  • What do you think about this answer? E-mail the editors at editor@searchDatabase.com with your feedback.
  • The Best Oracle Web Links: tips, tutorials, scripts, and more.
  • Have an Oracle or SQL tip to offer your fellow DBAs and developers? The best tips submitted will receive a cool prize. Submit your tip today!
  • Ask your technical Oracle and SQL questions -- or help out your peers by answering them -- in our live discussion forums.
  • Ask the Experts yourself: Our SQL, database design, Oracle, SQL Server, DB2, metadata, object-oriented and data warehousing gurus are waiting to answer your toughest questions.

This was last published in March 2002

Dig Deeper on Oracle database design and architecture

PRO+

Content

Find more PRO+ content and other member only offers, here.

Have a question for an expert?

Please add a title for your question

Get answers from a TechTarget expert on whatever's puzzling you.

You will be able to add details on the next page.

Start the conversation

Send me notifications when other members comment.

By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy

Please create a username to comment.

-ADS BY GOOGLE

SearchDataManagement

SearchBusinessAnalytics

SearchSAP

SearchSQLServer

TheServerSide.com

SearchDataCenter

SearchContentManagement

SearchFinancialApplications

Close