Thread: Delete 1 Record of 2 Duplicate Records

How do I delete only 1 of the duplicate records?

column_name | column_id
---------------------+--------------test1                 |         5test1                 |         5


I've tried this:

tmp_test=# delete from test where column_id = 5 limit 1;
ERROR:  parser: parse error at or near "limit"

I'm using version 7.2.1

Thank you.

On Thu, 30 Jan 2003 val@webtribe.net wrote:

> How do I delete only 1 of the duplicate records?

Do

select oid,* from test where column_id = 5;

then choose which oid to delete
and do

delete from test where oid = ...;

>
>
>  column_name | column_id
> ---------------------+--------------
>  test1                 |         5
>  test1                 |         5
>
>
> I've tried this:
>
> tmp_test=# delete from test where column_id = 5 limit 1;
> ERROR:  parser: parse error at or near "limit"
>
> I'm using version 7.2.1
>
> Thank you.
>
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> http://www.postgresql.org/users-lounge/docs/faq.html
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If they are truly identical, then you must use the hidden 'oid' column to 
differentiate the two. No need to peek at the oid, just do this:

DELETE FROM test WHERE oid = (SELECT oid FROM test WHERE column_id=5 LIMIT 1);

- --
Greg Sabino Mullane greg@turnstep.com
PGP Key: 0x14964AC8 200301301006

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greg@turnstep.com writes:
> If they are truly identical, then you must use the hidden 'oid' column to 
> differentiate the two. No need to peek at the oid, just do this:

> DELETE FROM test WHERE oid = (SELECT oid FROM test WHERE column_id=5 LIMIT 1);

Also, if you're unfortunate enough to have this problem in a table with
no OID column, you can play the same trick with the ctid column, which
always exists (it's the physical location of the tuple).  ctid is
dangerous to use for most purposes, because it's not stable over UPDATE
or VACUUM FULL, but it works perfectly well for this kind of problem.
        regards, tom lane