Thread: calculated identity field in views, again...
I asked this question several weeks ago, but nobody proposed a solution, so I am repeating the same question again... I have an MS Access front-end for a database on PostgreSQL. I could use pass-through queries as record sources for reports and it works fine... Unfortunately, MS Access doesn't allow pass-through queries to be records sources for subforms. Therefore I tried to base subforms on regular JET queries on linked tables. It was too slow... Then I tried to base subforms on DAO recordset code generated from pass-through QueryDef objects. Although it worked, it was very unstable... Now it seems to me that POstgreSQL views are the best solution, but Access considers views as tables (!) and needs column with unique values. All those views are complicated queries on several tables, so I can't use any table's column as primary key. I need a calculated column in the view that Access will consider as primary key column. In regular tables, I use bigserial field, but how can I create calculated bigserial column in a view ? Thanks.
Zlatko Matic wrote: > I asked this question several weeks ago, but nobody proposed a solution, > so I am repeating the same question again... > I have an MS Access front-end for a database on PostgreSQL. > I could use pass-through queries as record sources for reports and it > works fine... > Unfortunately, MS Access doesn't allow pass-through queries to be > records sources for subforms. > Therefore I tried to base subforms on regular JET queries on linked > tables. It was too slow... > Then I tried to base subforms on DAO recordset code generated from > pass-through QueryDef objects. Although it worked, it was very unstable... > > Now it seems to me that POstgreSQL views are the best solution, but > Access considers views as tables (!) and needs column with unique values. > All those views are complicated queries on several tables, so I can't > use any table's column as primary key. I need a calculated column in the > view that Access will consider as primary key column. > In regular tables, I use bigserial field, but how can I create > calculated bigserial column in a view ? > > Thanks. > > ---------------------------(end of broadcast)--------------------------- > TIP 9: the planner will ignore your desire to choose an index scan if your > joining column's datatypes do not match > > Another option is to toss the MS Access altogether and program the front end entirely in VB. That is what we did. -- Kind Regards, Keith
"Zlatko Matic" <zlatko.matic1@sb.t-com.hr> writes:
> In regular tables, I use bigserial field, but how can I create calculated
> bigserial column in a view ?
You would have to create a sequence and reference it with
nextval('sequencename') in your view. But I doubt very much that it will do
anything useful.
It sounds like Access wants to be able to update records by looking them up by
primary key. In that case assigning a new value in your view will make
Postgres make up a brand new number that is utterly useless for finding the
record again later.
--
greg
I will try...if it will be useless, I will quite. Then the only solution
will be make-table query based on nested pass-through query, so I will be
working on local JET tables that will be refreshed from server on each
session. But I would like to avoid local tables, if possible...
How do I create sequence ?
----- Original Message -----
From: "Greg Stark" <gsstark@mit.edu>
To: "Zlatko Matic" <zlatko.matic1@sb.t-com.hr>
Cc: <pgsql-general@postgresql.org>; <pgsql-interfaces@postgresql.org>
Sent: Wednesday, May 04, 2005 7:11 AM
Subject: Re: [GENERAL] [INTERFACES] calculated identity field in views,
again...
> "Zlatko Matic" <zlatko.matic1@sb.t-com.hr> writes:
>
>> In regular tables, I use bigserial field, but how can I create calculated
>> bigserial column in a view ?
>
> You would have to create a sequence and reference it with
> nextval('sequencename') in your view. But I doubt very much that it will
> do
> anything useful.
>
> It sounds like Access wants to be able to update records by looking them
> up by
> primary key. In that case assigning a new value in your view will make
> Postgres make up a brand new number that is utterly useless for finding
> the
> record again later.
>
> --
> greg
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 4: Don't 'kill -9' the postmaster
>
You mean VB.NET ? ----- Original Message ----- From: "Keith Worthington" <KeithW@NarrowPathInc.com> To: "Zlatko Matic" <zlatko.matic1@sb.t-com.hr> Cc: <pgsql-general@postgresql.org>; <pgsql-interfaces@postgresql.org> Sent: Wednesday, May 04, 2005 5:58 AM Subject: Re: [INTERFACES] calculated identity field in views, again... > Zlatko Matic wrote: >> I asked this question several weeks ago, but nobody proposed a solution, >> so I am repeating the same question again... >> I have an MS Access front-end for a database on PostgreSQL. >> I could use pass-through queries as record sources for reports and it >> works fine... >> Unfortunately, MS Access doesn't allow pass-through queries to be records >> sources for subforms. >> Therefore I tried to base subforms on regular JET queries on linked >> tables. It was too slow... >> Then I tried to base subforms on DAO recordset code generated from >> pass-through QueryDef objects. Although it worked, it was very >> unstable... >> >> Now it seems to me that POstgreSQL views are the best solution, but >> Access considers views as tables (!) and needs column with unique values. >> All those views are complicated queries on several tables, so I can't use >> any table's column as primary key. I need a calculated column in the view >> that Access will consider as primary key column. >> In regular tables, I use bigserial field, but how can I create calculated >> bigserial column in a view ? >> >> Thanks. >> >> ---------------------------(end of broadcast)--------------------------- >> TIP 9: the planner will ignore your desire to choose an index scan if >> your >> joining column's datatypes do not match >> >> > > Another option is to toss the MS Access altogether and program the front > end entirely in VB. That is what we did. > > -- > Kind Regards, > Keith > > ---------------------------(end of broadcast)--------------------------- > TIP 2: you can get off all lists at once with the unregister command > (send "unregister YourEmailAddressHere" to majordomo@postgresql.org) >
>> Zlatko Matic wrote: >> >>> I asked this question several weeks ago, but nobody proposed a >>> solution, so I am repeating the same question again... >>> I have an MS Access front-end for a database on PostgreSQL. >>> I could use pass-through queries as record sources for reports and it >>> works fine... >>> Unfortunately, MS Access doesn't allow pass-through queries to be >>> records sources for subforms. >>> Therefore I tried to base subforms on regular JET queries on linked >>> tables. It was too slow... >>> Then I tried to base subforms on DAO recordset code generated from >>> pass-through QueryDef objects. Although it worked, it was very >>> unstable... >>> >>> Now it seems to me that POstgreSQL views are the best solution, but >>> Access considers views as tables (!) and needs column with unique >>> values. >>> All those views are complicated queries on several tables, so I can't >>> use any table's column as primary key. I need a calculated column in >>> the view that Access will consider as primary key column. >>> In regular tables, I use bigserial field, but how can I create >>> calculated bigserial column in a view ? >>> >>> Thanks. >>> >>> ---------------------------(end of broadcast)--------------------------- >>> TIP 9: the planner will ignore your desire to choose an index scan if >>> your >>> joining column's datatypes do not match >>> >>> >> >> Another option is to toss the MS Access altogether and program the >> front end entirely in VB. That is what we did. >> >> -- >> Kind Regards, >> Keith >> > Zlatko Matic wrote: > You mean VB.NET ? Actually we wrote our interface using VB6. -- Kind Regards, Keith
On Wed, May 04, 2005 at 10:56:25 +0200, Zlatko Matic <zlatko.matic1@sb.t-com.hr> wrote: > I will try...if it will be useless, I will quite. Then the only solution > will be make-table query based on nested pass-through query, so I will be > working on local JET tables that will be refreshed from server on each > session. But I would like to avoid local tables, if possible... Didn'y you ask this same question a week or two ago? I am pretty sure someone told you how to make access work with a view. > How do I create sequence ? You can't create a sequence for a view. You would need to have it in a table that is joined as part of the view.
Bruno Wolff III <bruno@wolff.to> writes:
> > How do I create sequence ?
>
> You can't create a sequence for a view. You would need to have it in a
> table that is joined as part of the view.
Sure you can. You can have any expression you want, including nextval('seq')
in your view. The problem is that every time you query it it will provide
different numbers. I can't see that being useful.
--
greg
--- Zlatko Matic <zlatko.matic1@sb.t-com.hr> wrote: > I asked this question several weeks ago, but nobody > proposed a solution, so > I am repeating the same question again... > I have an MS Access front-end for a database on > PostgreSQL. > I could use pass-through queries as record sources > for reports and it works > fine... > Unfortunately, MS Access doesn't allow pass-through > queries to be records > sources for subforms. Unless you use unbound form/controls. Which means handling everything in code, which might work out best for you, depending on what you want (this is effectively equivalent to the VB-only option which someone else mentioned). > Therefore I tried to base subforms on regular JET > queries on linked tables. > It was too slow... > Then I tried to base subforms on DAO recordset code > generated from > pass-through QueryDef objects. Although it worked, > it was very unstable... > > Now it seems to me that POstgreSQL views are the > best solution, but Access > considers views as tables (!) and needs column with > unique values. AFAIK a composite key (combination of several columns) should work ok for a primary key for Access. When linking to the view, just select the columns you want to use. Or are you saying that you tried this, and it didn't work? Alternatively, you could try including in your view definition the oid column for each of the constituent tables. If I understand right, oids are globally unique within your database. This assumes that you have created your tables with oids, which may not be the case. Basing a subform on a mult-table join sounds like odd database design. Perhaps if you can explain more about what you are trying to do, people can offer more suggestions. > All those views are complicated queries on several > tables, so I can't use > any table's column as primary key. I need a > calculated column in the view > that Access will consider as primary key column. > In regular tables, I use bigserial field, but how > can I create calculated > bigserial column in a view ? > > Thanks. > > > ---------------------------(end of > broadcast)--------------------------- > TIP 9: the planner will ignore your desire to choose > an index scan if your > joining column's datatypes do not match > __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
On Wed, May 04, 2005 at 11:47:12 -0400,
Greg Stark <gsstark@mit.edu> wrote:
> Bruno Wolff III <bruno@wolff.to> writes:
>
> > > How do I create sequence ?
> >
> > You can't create a sequence for a view. You would need to have it in a
> > table that is joined as part of the view.
>
> Sure you can. You can have any expression you want, including nextval('seq')
> in your view. The problem is that every time you query it it will provide
> different numbers. I can't see that being useful.
That is more or less what I meant. You can't usefully tie a sequence directly
to a view, the way you can tie one to a table.
Hello. Thanks for answers... After considering all proposed, I think that it is probably possible to give MS Acces some composite primary keys while linking views as tables, in order to help Access not to fall into "#deleted#", but it would take some extra time to experiment with every view. In meantime, I successfully implemented solution with local tables. Append queries based on pass-through queries are triggered and local tables are refreshed. It seems to be fast and reliable... Thank you anyway, maybe I will try something with views next time... ----- Original Message ----- From: "Jeff Eckermann" <jeff_eckermann@yahoo.com> To: "Zlatko Matic" <zlatko.matic1@sb.t-com.hr>; <pgsql-general@postgresql.org>; <pgsql-interfaces@postgresql.org> Sent: Wednesday, May 04, 2005 6:01 PM Subject: Re: [GENERAL] [INTERFACES] calculated identity field in views, again... > --- Zlatko Matic <zlatko.matic1@sb.t-com.hr> wrote: >> I asked this question several weeks ago, but nobody >> proposed a solution, so >> I am repeating the same question again... >> I have an MS Access front-end for a database on >> PostgreSQL. >> I could use pass-through queries as record sources >> for reports and it works >> fine... >> Unfortunately, MS Access doesn't allow pass-through >> queries to be records >> sources for subforms. > > Unless you use unbound form/controls. Which means > handling everything in code, which might work out best > for you, depending on what you want (this is > effectively equivalent to the VB-only option which > someone else mentioned). > >> Therefore I tried to base subforms on regular JET >> queries on linked tables. >> It was too slow... >> Then I tried to base subforms on DAO recordset code >> generated from >> pass-through QueryDef objects. Although it worked, >> it was very unstable... >> >> Now it seems to me that POstgreSQL views are the >> best solution, but Access >> considers views as tables (!) and needs column with >> unique values. > > AFAIK a composite key (combination of several columns) > should work ok for a primary key for Access. When > linking to the view, just select the columns you want > to use. Or are you saying that you tried this, and it > didn't work? > > Alternatively, you could try including in your view > definition the oid column for each of the constituent > tables. If I understand right, oids are globally > unique within your database. This assumes that you > have created your tables with oids, which may not be > the case. > > Basing a subform on a mult-table join sounds like odd > database design. Perhaps if you can explain more > about what you are trying to do, people can offer more > suggestions. > >> All those views are complicated queries on several >> tables, so I can't use >> any table's column as primary key. I need a >> calculated column in the view >> that Access will consider as primary key column. >> In regular tables, I use bigserial field, but how >> can I create calculated >> bigserial column in a view ? >> >> Thanks. >> >> >> ---------------------------(end of >> broadcast)--------------------------- >> TIP 9: the planner will ignore your desire to choose >> an index scan if your >> joining column's datatypes do not match >> > > __________________________________________________ > Do You Yahoo!? > Tired of spam? Yahoo! Mail has the best spam protection around > http://mail.yahoo.com > > ---------------------------(end of broadcast)--------------------------- > TIP 2: you can get off all lists at once with the unregister command > (send "unregister YourEmailAddressHere" to majordomo@postgresql.org) >
Ragnar Hafstað wrote: > On Wed, 2005-05-04 at 09:01 -0700, Jeff Eckermann wrote: > > >> If I understand right, oids are globally >>unique within your database. > > > I am affraid not oids are globally unique within the catalog. > > gnari > > > > ---------------------------(end of broadcast)--------------------------- > TIP 4: Don't 'kill -9' the postmaster
"Joshua D. Drake" <jd@commandprompt.com> writes:
> Ragnar Hafsta� wrote:
>> On Wed, 2005-05-04 at 09:01 -0700, Jeff Eckermann wrote:
>>> If I understand right, oids are globally
>>> unique within your database.
>>
>> I am affraid not
> oids are globally unique within the catalog.
... until the OID generator wraps around, and then they aren't so
unique anymore.
You can enforce uniqueness within a particular table by creating
a unique index on the OID column, but that's about as much as
you can guarantee.
regards, tom lane
On Wed, 2005-05-04 at 09:01 -0700, Jeff Eckermann wrote: > If I understand right, oids are globally > unique within your database. I am affraid not gnari