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* Syntax question: use of join/using with fully qualified table name
@ 2008-01-28 00:49 Bryce Nesbitt <bryce1@obviously.com>
0 siblings, 2 replies; 3+ messages in thread
From: Bryce Nesbitt @ 2008-01-28 00:49 UTC (permalink / raw)
To: pgsql-sql
I've got a join where a certain column name appears twice:
select username,last_name from eg_member join eg_membership using
(member_id) join eg_account using (account_id) join eg_person using
(person_id);
ERROR: common column name "person_id" appears more than once in left table
My first inclination was to fully quality the table name. Why would
this not be acceptable syntax?
select username,last_name from eg_member join eg_membership using
(member_id) join eg_account using (account_id) join eg_person using
(eg_member.person_id);
ERROR: syntax error at or near "." at character 145
Of course I eventually wrote it:
select username,last_name from eg_member join eg_membership using (member_id) join eg_account using (account_id) join eg_person on eg_member.person_id=eg_person.person_id';
PostgreSQL 8.1.9 on i686-redhat-linux-gnu, compiled by GCC gcc (GCC) 4.1.1 20070105 (Red Hat 4.1.1-51)
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Visit http://www.obviously.com/
^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: Syntax question: use of join/using with fully qualified table name
@ 2008-01-28 01:43 Martin Marques <martin@marquesminen.com.ar>
parent: Bryce Nesbitt <bryce1@obviously.com>
1 sibling, 0 replies; 3+ messages in thread
From: Martin Marques @ 2008-01-28 01:43 UTC (permalink / raw)
To: Bryce Nesbitt <bryce1@obviously.com>; +Cc: pgsql-sql
Bryce Nesbitt escribió:
> I've got a join where a certain column name appears twice:
>
> select username,last_name from eg_member join eg_membership using
> (member_id) join eg_account using (account_id) join eg_person using
> (person_id);
> ERROR: common column name "person_id" appears more than once in left table
>
>
> My first inclination was to fully quality the table name. Why would
> this not be acceptable syntax?
>
> select username,last_name from eg_member join eg_membership using
> (member_id) join eg_account using (account_id) join eg_person using
> (eg_member.person_id);
> ERROR: syntax error at or near "." at character 145
Did you read the manual?
USING (join_column [, ...])
A clause of the form USING ( a, b, ... ) is shorthand for ON
left_table.a = right_table.a AND left_table.b = right_table.b .... Also,
USING implies that only one of each pair of equivalent columns will be
included in the join output, not both.
^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: Syntax question: use of join/using with fully qualified table name
@ 2008-01-28 01:45 Tom Lane <tgl@sss.pgh.pa.us>
parent: Bryce Nesbitt <bryce1@obviously.com>
1 sibling, 0 replies; 3+ messages in thread
From: Tom Lane @ 2008-01-28 01:45 UTC (permalink / raw)
To: Bryce Nesbitt <bryce1@obviously.com>; +Cc: pgsql-sql
Bryce Nesbitt <bryce1@obviously.com> writes:
> I've got a join where a certain column name appears twice:
> select username,last_name from eg_member join eg_membership using
> (member_id) join eg_account using (account_id) join eg_person using
> (person_id);
> ERROR: common column name "person_id" appears more than once in left table
> My first inclination was to fully quality the table name. Why would
> this not be acceptable syntax?
Because USING is defined as joining common column names. It is driven
entirely by the column names, not any "qualification", and it needs to
have well-defined behavior. The SQL92 spec saith
<named columns join> ::=
USING <left paren> <join column list> <right paren>
<join column list> ::= <column name list>
<column name list> ::=
<column name> [ { <comma> <column name> }... ]
<column name> ::= <identifier>
...
b) If a <named columns join> is specified, then every <column
name> in the <join column list> shall be the <column name>
of exactly one column of T1 and the <column name> of exactly
one column of T2.
regards, tom lane
^ permalink raw reply [nested|flat] 3+ messages in thread
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2008-01-28 00:49 Syntax question: use of join/using with fully qualified table name Bryce Nesbitt <bryce1@obviously.com>
2008-01-28 01:43 ` Martin Marques <martin@marquesminen.com.ar>
2008-01-28 01:45 ` Tom Lane <tgl@sss.pgh.pa.us>
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