Except operation

From: Satyajeet Seth <csa98016(at)cse(dot)iitd(dot)ernet(dot)in>
To: pgsql-novice(at)postgreSQL(dot)org
Cc: pgsql-sql(at)postgreSQL(dot)org
Subject: Except operation
Date: 1999-12-01 18:40:13
Message-ID: Pine.LNX.4.10.9912020004510.3321-100000@vibhas.cse.iitd.ernet.in
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Hi
The query:
select * from webdata except select * from webdata1;
takes abysmally long .How can I optimise it?
The particulars are:

tracedb=> \d webdata
Table = webdata
+----------------------------------+----------------------------------+-------+
| Field | Type |
Length|
+----------------------------------+----------------------------------+-------+
| tid | int4 |
4 |
| itemid | int4 |
4 |
| ordering | int4 |
4 |
+----------------------------------+----------------------------------+-------+

tracedb=> \d webdata1
Table = webdata1
+----------------------------------+----------------------------------+-------+
| Field | Type |
Length|
+----------------------------------+----------------------------------+-------+
| tid | int4 |
4 |
| itemid | int4 |
4 |
| ordering | int4 |
4 |
+----------------------------------+----------------------------------+-------+
tracedb=> select count(*) from webdata;
count
-----
91155
(1 row)

tracedb=> select count(*) from webdata1;
count
-----
9550
(1 row)

Regards
Satya

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