Thread: Delete from Join
Hello,
Is it possible to use a join keyword in a delete?
For example:
DELETE FROM data_table1
using data_table2 INNER JOIN
data_table1 ON data_table1.fkey = data_table2.pkey;
It is not directly mentioned in the delete syntax but the delete refers
to the select clause where JOIN is valid.
G
--- On Wed, 7/2/08, Gwyneth Morrison <postgres@toadware.ca> wrote: > From: Gwyneth Morrison <postgres@toadware.ca> > Subject: [GENERAL] Delete from Join > To: pgsql-general@postgresql.org > Date: Wednesday, July 2, 2008, 3:15 PM > Hello, > > Is it possible to use a join keyword in a delete? > > For example: > > DELETE FROM data_table1 > using data_table2 INNER JOIN > data_table1 ON data_table1.fkey = > data_table2.pkey; > > > It is not directly mentioned in the delete syntax but the > delete refers > to the select clause where JOIN is valid. > > G > i have a example delete from t1 a using t2 b where a.id = b.oid A standard way to do it is delete from t1 a where id in (select a.id from t1 a inner join t2 b on (a.id = b.oid))
<div class="moz-text-plain" wrap="true" graphical-quote="true" style="font-family: -moz-fixed; font-size: 12px;" lang="x-western"> --- On Wed, 7/2/08, Gwyneth Morrison <a class="moz-txt-link-rfc2396E" href="mailto:postgres@toadware.ca"><postgres@toadware.ca> wrote: > From: Gwyneth Morrison <a class="moz-txt-link-rfc2396E" href="mailto:postgres@toadware.ca"><postgres@toadware.ca> > Subject: [GENERAL] Delete from Join > To: <a class="moz-txt-link-abbreviated" href="mailto:pgsql-general@postgresql.org">pgsql-general@postgresql.org > Date: Wednesday, July 2, 2008, 3:15 PM > Hello, > > Is it possible to use a join keyword in a delete? > > For example: > > DELETE FROM data_table1 > using data_table2 INNER JOIN > data_table1 ON data_table1.fkey = > data_table2.pkey; > > > It is not directly mentioned in the delete syntax but the > delete refers > to the select clause where JOIN is valid. > > G > >i have a example >delete from t1 a using t2 b where a.id = b.oid >A standard way to do it is >delete from t1 a where id in (select a.id from t1 a inner join t2 b on (a.id = b.oid)) Thank you for your reply, You are absolutely correct, it IS the standard way. What I am actually trying to do here is write a program to convert MS SQL to Postgres. I have had quite a bit of success so far, but this is a sticking point. Apparently using the JOIN keyword directly in a delete statement is valid in MS. I am trying to determine if it is valid in postgres which I figure it is not but cannot find it exactly in the documentation. So I guess the real question is, can the JOIN keyword be used directly in a delete as above. G -- Sent via pgsql-general mailing list (<a class="moz-txt-link-abbreviated" href="mailto:pgsql-general@postgresql.org">pgsql-general@postgresql.org) To make changes to your subscription: <a class="moz-txt-link-freetext" href="http://www.postgresql.org/mailpref/pgsql-general">http://www.postgresql.org/mailpref/pgsql-general
Take a look here, in the notes section: http://www.postgresql.org/docs/8.3/interactive/sql-delete.html on the using keyword.
Scott Marlowe wrote: > Take a look here, in the notes section: > > http://www.postgresql.org/docs/8.3/interactive/sql-delete.html > > on the using keyword. > > Thank you for your reply Scott, I guess this is where the confusion started for me. It says here in your reference that the using clause is not standard but that is fine as I am doing a subst. MS actually allows: DELETE from table from table..... I change the second from to a using and it works fine most of the time. What I am actually trying to get past is: DELETE FROM data_table1 using data_table2 INNER JOIN data_table1 ON data_table1.fkey = data_table2.pkey; Where the INNER JOIN keyword is used in the delete. In the documentation section you cited, they refer to the from clause in the usinglist. The from clause link there refers to select which states that a join keyword is valid in a from clause. What I have found is it sometimes compiles but doesn't work. I am just seeking verification if it is supposed to work. Gwyneth
--- On Wed, 7/2/08, Gwyneth Morrison <gwynethm@toadware.ca> wrote: > From: Gwyneth Morrison <gwynethm@toadware.ca> > Subject: Re: [GENERAL] Delete from Join > To: pgsql-general@postgresql.org > Date: Wednesday, July 2, 2008, 7:12 PM > --- On Wed, 7/2/08, Gwyneth Morrison > <postgres@toadware.ca> wrote: > > > > > From: Gwyneth Morrison <postgres@toadware.ca> > > Subject: [GENERAL] Delete from Join > > To: pgsql-general@postgresql.org > > Date: Wednesday, July 2, 2008, 3:15 PM > > Hello, > > > > Is it possible to use a join keyword in a delete? > > > > For example: > > > > DELETE FROM data_table1 > > using data_table2 INNER JOIN > > data_table1 ON > data_table1.fkey = > > data_table2.pkey; > > > > > > It is not directly mentioned in the delete syntax but > the > > delete refers > > to the select clause where JOIN is valid. > > > > G > > > > > > >i have a example > > >delete from t1 a using t2 b where a.id = b.oid > > >A standard way to do it is > > >delete from t1 a where id in (select a.id from t1 a > inner join t2 b on (a.id = b.oid)) > > > Thank you for your reply, > > You are absolutely correct, it IS the standard way. > > What I am actually trying to do here is write a program to > convert MS SQL to Postgres. > I have had quite a bit of success so far, but this is a > sticking point. > > Apparently using the JOIN keyword directly in a delete > statement is valid in MS. > I am trying to determine if it is valid in postgres which I > figure it is not but cannot > find it exactly in the documentation. > > So I guess the real question is, can the JOIN keyword be > used directly in a delete as above. > > G > > i have the same problem. i try use JOIN keyword in DELETE syntax but dont work. I assume cant use JOIN keywork
Gwyneth Morrison <gwynethm@toadware.ca> writes:
> What I am actually trying to get past is:
> DELETE FROM data_table1
> using data_table2 INNER JOIN
> data_table1 ON data_table1.fkey =
> data_table2.pkey;
The equivalent to that in Postgres would be
DELETE FROM data_table1
USING data_table2
WHERE data_table1.fkey = data_table2.pkey;
The fundamental issue here is that MSSQL expects the USING clause to
contain a second reference to the delete target table, whereas PG
does not --- if you write the table name again, that's effectively
a self-join and you probably won't get the behavior you want.
You can use JOIN syntax in USING in Postgres, but only for situations
where the query really involves three or more tables.
regards, tom lane
Tom Lane wrote:
Gwyneth Morrison <gwynethm@toadware.ca> writes:
What I am actually trying to get past is:
DELETE FROM data_table1
using data_table2 INNER JOIN
data_table1 ON data_table1.fkey =
data_table2.pkey;
The equivalent to that in Postgres would be
DELETE FROM data_table1
USING data_table2
WHERE data_table1.fkey = data_table2.pkey;
The fundamental issue here is that MSSQL expects the USING clause to
contain a second reference to the delete target table, whereas PG
does not --- if you write the table name again, that's effectively
a self-join and you probably won't get the behavior you want.
You can use JOIN syntax in USING in Postgres, but only for situations
where the query really involves three or more tables.
regards, tom lane
Thank you Tom,
That was exactly what I needed to know and yes it does work.
I do know about the using/from clause and and the second table
reference.
Sorry about the above example, I cut it from something much larger to
try and
get my point across. Yes it is invalid. I should be more careful.
I do have another question I will post as a separate posting.
Gwyneth