Re: Diff. between UNION and UNION ALL

From: AMARENDRA B NETTEM <nettama_at_charlie.cns.iit.edu>
Date: 1997/03/01
Message-ID: <01bc25e3$0d7fbb50$81a757c6@vanaja>#1/1

Hi Naren,

  For example if you have two tables named T1 and T2, then

...........................................

Table T1                       table T2
---------                     -----------
ename varchar2(12)             name   varchar2(12)

 A                               C
 B                               D

 C
 D

..........................................

SELECT ename FROM t1
 UNION
SELECT name FROM t2
 RESULT : A B C D ( DISTINCT VALUES)

.............................................

SELECT ename FROM t1
 UNION ALL
SELECT name FROM t2
 RESULT : A B C D C D ( including DUPLICATE VALUES).

............................................

Hope this helps

-- 
    AMARENDRA B NETTEM
    ORACLE CONSULTANT
    WHITTMAN-HART INC., CHICAGO
    (http://www.iit.edu/~nettama)


Naren Chintala <naren_at_mink.att.com> wrote in article
<33173071.8F9_at_mink.att.com>...


> Hi,

> 

> What's the difference between UNION and UNION ALL (in a SELECT

> statement). I don't find any info on this in the Oracle manuals. Would

> someone explain this with a simple example.

> 

> TIA

> 

> Naren

> 

 

Received on Sat Mar 01 1997 - 00:00:00 CST