I am wondering how to do this simple mysql task in postgres. Any hints?

Thanks,
Sean


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* Sean Davis <sdavis2 (AT) mail (DOT) nih.gov> [2004-10-21 12:26:47 -0400]:

This reply from Ron Johnson seems to suffice:

http://archives.postgresql.org/pgsql...5/msg00102.php

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Steven Klassen - Lead Programmer
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I'm not sure why this even matters. You do DROP TABLE on a table that
doesn't exist, all that will happen is that you will get an error back
but your program will continue on it's merry way anyways. The only thing
IF EXISTS would give you is the suppression of the error message.


Steven Klassen wrote:

Point taken. However, in a perl/DBI setting, the program does die unless I
explicitly trap the error, etc. So, it is a convenience, true enough, but
not an issue that I had to deal with in MySQL, so just thought I would ask.

Sean


-----Original Message-----
From: William Yu
To: pgsql-novice (AT) postgresql (DOT) org
Sent: 10/25/2004 2:05 PM
Subject: Re: [NOVICE] DROP TABLE IF EXISTS

I'm not sure why this even matters. You do DROP TABLE on a table that
doesn't exist, all that will happen is that you will get an error back
but your program will continue on it's merry way anyways. The only thing

IF EXISTS would give you is the suppression of the error message.


Steven Klassen wrote:

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http://archives.postgresql.org

That's a new one to me. I use perl/DBI also and my scripts just ignore
errors w/o any error trapping. Maybe my defaults are set to ignore
errors. I only trap errors when I there's a possibility of catastrophic
failure. (Example, DB is down -- SELECT * FROM zzz returns an error so
the row count is 0 -- page looks normal except there's no content versus
some generic apache error message.)




Davis, Sean (NIH/NHGRI) wrote:

--- William Yu <wyu (AT) talisys (DOT) com> escribió:


what about the Ron Johnson solution?
if exists (select 1 from pg_tables where tablename =
"thetable")
regards,
Jaime Casanova

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Jaime,

Thanks for the reply.

On Oct 26, 2004, at 4:51 PM, Jaime Casanova wrote:
Actually, Ron gave some other possibilities, but the query above does
NOT work (and was the original source of the question). Just for
information, here is a function that I had come up with that works. It
returns 1 or 0 just as a sanity check.

create or replace function drop_if_exists (text) returns INTEGER AS '
DECLARE
tbl_name ALIAS FOR $1;
BEGIN
IF (select count(*) from pg_tables where tablename=$1) THEN EXECUTE
''DROP TABLE '' || $1;
RETURN 1;
END IF;
RETURN 0;
END;
'
language 'plpgsql';

Sean


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