TClientDataSet RecNo

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5 total messages Started by mpowell Fri, 30 Mar 2001 17:00

#603

Author: mpowell
Date: Fri, 30 Mar 2001 17:00

17 lines
1387 bytes

I have a record set that I would like to reorder. Is the RecNo property the
property that will correctly do so? IOW, If I make any changes to RecNo will
the record numbers for the remaining records change accordingly.

For example, say I have the following record set.

NAME; ID; RECNO
JOHN; 101; 1
PAUL; 201; 2
RINGO; 301; 3

Say I change RINGO to RECNO=1. Does this then change JOHN to RECNO=2 and
PAUL to RECNO=3? Alternately, what happens if I change PAUL to RECNO=3? What
precisely is the effect of changing RECNO in this manner?

Thanks in advance.

Re: TClientDataSet RecNo

#606

Author: mpowell
Date: Wed, 04 Apr 2001 20:10

36 lines
1788 bytes

Hello,

I'd really appreciate an answer to this. Is it possible to reorganize
(perhaps even swap) a record within a data set? The RecNo property isn't
quite what I had in mind, as it seems only to operate on the cursor. I would
like to move the record, not the cursor, within a data set.

Thanks.


"mpowell" <mike.powell@transcore.com> wrote in message
news:3ac4bbb2$1_1@dnews...
>
> I have a record set that I would like to reorder. Is the RecNo property
the
> property that will correctly do so? IOW, If I make any changes to RecNo
will
> the record numbers for the remaining records change accordingly.
>
> For example, say I have the following record set.
>
> NAME; ID; RECNO
> JOHN; 101; 1
> PAUL; 201; 2
> RINGO; 301; 3
>
> Say I change RINGO to RECNO=1. Does this then change JOHN to RECNO=2 and
> PAUL to RECNO=3? Alternately, what happens if I change PAUL to RECNO=3?
What
> precisely is the effect of changing RECNO in this manner?
>
> Thanks in advance.
>
>
>

Re: TClientDataSet RecNo

#607

Author: mpowell
Date: Wed, 04 Apr 2001 20:33

47 lines
2188 bytes

Another possibility is that I can perform whatever updates on the client
data set while it is "in place". Is it possible to sort a record set while
it is in place, or prior to applying any changes?


"mpowell" <mike.powell@transcore.com> wrote in message
news:3acb80f0_2@dnews...
>
> Hello,
>
> I'd really appreciate an answer to this. Is it possible to reorganize
> (perhaps even swap) a record within a data set? The RecNo property isn't
> quite what I had in mind, as it seems only to operate on the cursor. I
would
> like to move the record, not the cursor, within a data set.
>
> Thanks.
>
>
> "mpowell" <mike.powell@transcore.com> wrote in message
> news:3ac4bbb2$1_1@dnews...
> >
> > I have a record set that I would like to reorder. Is the RecNo property
> the
> > property that will correctly do so? IOW, If I make any changes to RecNo
> will
> > the record numbers for the remaining records change accordingly.
> >
> > For example, say I have the following record set.
> >
> > NAME; ID; RECNO
> > JOHN; 101; 1
> > PAUL; 201; 2
> > RINGO; 301; 3
> >
> > Say I change RINGO to RECNO=1. Does this then change JOHN to RECNO=2 and
> > PAUL to RECNO=3? Alternately, what happens if I change PAUL to RECNO=3?
> What
> > precisely is the effect of changing RECNO in this manner?
> >
> > Thanks in advance.
> >
> >
> >
>
>

Re: TClientDataSet RecNo

#608

Author: Mark Cashman
Date: Wed, 04 Apr 2001 22:57

23 lines
1828 bytes

Hi!

Recno means nothing to most DBMS which, for a variety of reasons may or
may not store records in any sort of "real" order (hash tables, for
instance have no real order).

Indexes give a view of the same records in the order the index decrees,
and each index has a different "order". In addition, in a real
client-server database, a single insertion could force recounting and
renumbering of a potentially prohibitive number of records.

To create a sequenced table you will need to have a sequence number
field and you will need to manage resequencing. It is a moderately
complex problem, but it can be done.

------
Mark Cashman (TeamB - C++ Builder), creator of The Temporal Doorway at
http://www.temporaldoorway.com
- Original digital art, writing, music and more -
C++ Builder / JBuilder Tips and The C++ Builder Programmer's Webring
(Join us!)
http://www.temporaldoorway.com/programming/index.htm
------

Re: TClientDataSet RecNo

#610

Author: mpowell
Date: Thu, 05 Apr 2001 14:21

36 lines
2218 bytes

Your suggestion is basically the approach I have taken. I was just wondering
if there was an "elegant" solution based on the data set itself. Though, now
there appears as though there isn't unless I were to subclass TClientDataSet
or something to perform such rearranging behavior.

Cheers!


"Mark Cashman" <mcashman@temporaldoorway.com> wrote in message
news:3ACBA6CC.A514FC7F@temporaldoorway.com...
> Hi!
>
> Recno means nothing to most DBMS which, for a variety of reasons may or
> may not store records in any sort of "real" order (hash tables, for
> instance have no real order).
>
> Indexes give a view of the same records in the order the index decrees,
> and each index has a different "order". In addition, in a real
> client-server database, a single insertion could force recounting and
> renumbering of a potentially prohibitive number of records.
>
> To create a sequenced table you will need to have a sequence number
> field and you will need to manage resequencing. It is a moderately
> complex problem, but it can be done.
>
> ------
> Mark Cashman (TeamB - C++ Builder), creator of The Temporal Doorway at
> http://www.temporaldoorway.com
> - Original digital art, writing, music and more -
> C++ Builder / JBuilder Tips and The C++ Builder Programmer's Webring
> (Join us!)
> http://www.temporaldoorway.com/programming/index.htm
> ------
>
>

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