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From: Rajesh Kumar Mallah. <mallah@trade-india.com>
To: pgsql-sql@postgresql.org
Subject: why the difference?
Date: Thu, 21 Nov 2002 12:17:09 +0530
Message-ID: <200211211217.09970.mallah@trade-india.com> (raw)


Hi folk,

i am finding something mysterious in SQL can anyone explain?

consider the SQL:

tradein_clients=# select distinct on  (amount,co_name,city)  category_id,amount,co_name,city from eyp_listing 
where keywordidx ## 'vegetable'  and  category_id=781 ;

 category_id | amount |          co_name          |    city
-------------+--------+---------------------------+------------
         781 |      0 | ANURADHA EXPORTS          | CHENNAI
         781 |      0 | R.K.INTERNATIONAL         | CHENNAI
         781 |      0 | SAI IMPEX                 | MUMBAI
         781 |      0 | TRIMA ENTERPRISES         | CHENNAI
         781 |      0 | UNIQUE DEHYDRATES LIMITED | AHMEDABAD
         781 |   5000 | RSV EXPORT                | COIMBATORE
(6 rows)


lets remove the contraint "category_id=781" and store the output in a table "t_a".

tradein_clients=# CREATE TABLE t_a AS select distinct on  (amount,co_name,city)  category_id,amount,co_name,city from 
eyp_listing  where keywordidx ## 'vegetable'  ;

then when i select from t_a with category_id=781 i have less secords

tradein_clients=# SELECT * from t_a where category_id=781;
 category_id | amount |          co_name          |    city
-------------+--------+---------------------------+------------
         781 |      0 | R.K.INTERNATIONAL         | CHENNAI
         781 |      0 | SAI IMPEX                 | MUMBAI
         781 |      0 | UNIQUE DEHYDRATES LIMITED | AHMEDABAD
         781 |   5000 | RSV EXPORT                | COIMBATORE
(4 rows)


Can anyone please explain the difference?


Regds
Mallah.








-- 
Rajesh Kumar Mallah,
Project Manager (Development)
Infocom Network Limited, New Delhi
phone: +91(11)6152172 (221) (L) ,9811255597 (M)

Visit http://www.trade-india.com ,
India's Leading B2B eMarketplace.





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