From: Bruce Momjian <pgman@candle.pha.pa.us>
Message-Id: <200208140312.g7E3CI124506@candle.pha.pa.us>
Subject: ANSI join types
In-Reply-To: <200208011633.g71GXQu02723@candle.pha.pa.us>
To: PostgreSQL-documentation <pgsql-docs@postgresql.org>
Date: Tue, 13 Aug 2002 23:12:18 -0400 (EDT)
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I got this list from Gavin Roy's presentation at O'Reilly.  Is there a
good spot for this summary?

Also, I can not find documentation on UNION JOINS in our docs.

---------------------------------------------------------------------------

Bruce Momjian wrote:
>    SELECT
>      * JOINS
>        
>      * Cross: All combinations of rows are used
>      * Inner: Only rows where matches are found are retained
>      * Left (Outer): Returns all rows from table A, matched or not, and
>        only rows from table B where matches are found
>      * Right (Outer): Inverse of Left, returns all rows from table B and
>        only matches from table A
>      * Full: A combination of left and right.  Where matches are not
>        found, NULLs fill the columns of the other table
>      * Union: This is different than the UNION operator used to merge the
>        output of multiple queries.  This is the inverse of an Inner, only
>        rows are returned when no matches are found
> 
> -- 
>   Bruce Momjian                        |  http://candle.pha.pa.us
>   pgman@candle.pha.pa.us               |  (610) 853-3000
>   +  If your life is a hard drive,     |  830 Blythe Avenue
>   +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026
> 

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073