From: Achilleas Mantzios <achill@matrix.gatewaynet.com>
Organization: Dynacom Tankers Mgmt
To: pgsql-sql@postgresql.org
Subject: Re: SQL gotcha
Date: Tue, 15 Feb 2011 09:41:11 +0200
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Cc: "Dean Gibson (DB Administrator)" <postgresql@ultimeth.com>
References: <4D59BAD5.4090306@ultimeth.com>
In-Reply-To: <4D59BAD5.4090306@ultimeth.com>
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=CE=A3=CF=84=CE=B9=CF=82 Tuesday 15 February 2011 01:29:25 =CE=BF/=CE=B7 De=
an Gibson (DB Administrator) =CE=AD=CE=B3=CF=81=CE=B1=CF=88=CE=B5:
> As you all know, when you specify an alias for a table or column name,=20
> the keyword "AS" is usually optional.  I personally like to always=20
> include the "AS" keyword, if for no other reason than readability, and I=
=20
> presume that always using "AS" might catch some syntactic errors as well.
>=20
> However, recently I ran across a statement where the optionality of the=20
> "AS" keyword caused me some grief:
>=20
>     SELECT ... FROM aaa LEFFT JOIN bbb WHERE ...
>=20
> Note the (unintentional) misspelling of the keyword "LEFT".  PostgreSQL=20
> took "LEFFT" to be an alias for table "aaa" and silently accepted the=20
> statement;  naturally I did not get the results I expected !!
>=20
> If PostgreSQL had an option to always require the "AS", that would have=20
> caught this error.  Is there any interest in PostgreSQL having any=20
> "pedantic"-type options, like many C/C++ compilers do?
>=20

Actually PostgreSQL seems to endorse the usage of "AS" more than the SQL st=
andard requires.
http://www.postgresql.org/docs/8.3/interactive/sql-select.html

"The AS Key Word

In the SQL standard, the optional key word AS is just noise and can be omit=
ted without affecting the meaning.=20
The PostgreSQL parser requires this key word when renaming output columns b=
ecause the type extensibility features=20
lead to parsing ambiguities without it. AS is optional in FROM items, howev=
er. "

=2D-=20
Achilleas Mantzios