From: | Guru Prasad <pnguruji(at)yahoo(dot)com> |
---|---|
To: | "pgsql-sql(at)postgresql(dot)org" <pgsql-sql(at)postgresql(dot)org> |
Subject: | How NULL is interpreted in Pgsql |
Date: | 2001-05-15 08:08:17 |
Message-ID: | Pine.LNX.4.20.0105151323560.16374-100000@Larry.bks |
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Lists: | pgsql-sql |
Dear Friends,
I created a table with no 'unique constraints' which is depicted as
follows.
create table junk (id int, name varchar);
Then, i inserted some records into the table. My table contents is listed
below.
id | name
-------------+------
1001.000000 | bolt
1002.000000 | nut
1003.000000 |
11.000000 | screw
| cutter
| cutting table
Then, i gave a select query for the above table. The select query is
'select * from junk where id != 11';
To my surprise, it displayed all the records except those which had
'NULL' in the 'id' field.
How is that possible ? (I mean it should displayed all the records except
the matching condition).
But, if i set PRIMARY KEY constraint to 'junk' table then it displays all
the records (I can't say NULL here, but i can say '0').
How NULL is processed in Postgres.
Could any one has some clue.
Regards,
guru.
bk SYSTEMS (P) Ltd.
P . N . G U R U P R A S A D
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