Date: Tue, 29 Jun 2004 20:17:42 +0400
From: "Alexander M. Pravking" <fduch@antar.bryansk.ru>
To: pgsql-sql@postgresql.org
Subject: UPDATE ... WHERE (subselect on the same table)
Message-ID: <20040629161742.GA73173@dyatel.antar.bryansk.ru>
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I was looking for how can I give an alias for the table being updated
(something like UPDATE table_name table_alias SET ...), but the current
syntax doesn't allow that.

What I need is to:

fduch=# SELECT * from test order by typ, name;
 typ | name | x
-----+------+---
   1 | bar  |
   1 | baz  |
   1 | foo  |
   2 | baz  |
   2 | foo  |
(5 rows)

fduch=# UPDATE test SET x = 't'
fduch-# where typ = 1 and exists (
fduch(# SELECT 1 from test t2
fduch(# where t2.typ = 2 and t2.name = test.name
fduch(# );
UPDATE 2
fduch=# SELECT * from test order by typ, name;
 typ | name | x
-----+------+---
   1 | bar  |
   1 | baz  | t
   1 | foo  | t
   2 | baz  |
   2 | foo  |
(5 rows)

So I have two questions:
Q1, cognitive. Why the alias for the updated table is restricted?
Is there any reason for that or it's just not implemented?

Q2, vital. Can I be sure that the syntax I used here will work
correctly, i.e. will the "test.name" always refer the column in outer
table, not inner (t2)?

Thanks in advance.

-- 
Fduch M. Pravking