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From: Gary Stainburn <gary.stainburn@ringways.co.uk>
Organization: Ringways Garages Ltd
To: pgsql-sql@postgresql.org
Subject: Re: simple update from select ??
Date: Mon, 7 Mar 2005 14:44:31 +0000
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References: <200503071228.39699.gary.stainburn@ringways.co.uk>
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On Monday 07 March 2005 12:28 pm, you wrote:
> Hi folks
>
> I've got a table of pieces of equipment.
> One piece of equipment may be owned by another piece of equipment,
> and may own multiple other pieces.
>
> To hold the relationship I have a piece_pieces table holding the
> owner (pp_id) part id and the owned part ids (pp_part).
>
> I'v realised I can store this within the original table so I've added
> an owner attribute.  I need to now populate this now from the other
> table, but I can't work out how.
>
> I've got  pieces table
>
> p_id		-- part id
> p_owner	-- new owner attribute
>
> piece_pieces table
>
> pp_id	-- id of owner
> pp_part	-- id of owned

For my own future reference as much as anything, here's the required 
statement, which is a syntactically corrected version of a suggestion 
by Sean Davis

update pieces set p_owner=piece_pieces.pp_id from piece_pieces where 
piece_pieces.pp_part=pieces.p_id;

Under Sean's suggestion I did this inside a transaction block so I could 
check that it did what I wanted.
-- 
Gary Stainburn
 
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