using Tbufdataset as memtable
lazarus / 16-Databases

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mangakissa · 2013-11-13 19:24

Im Delphi I'm very font of using VirtualTable (memorytable). With
Virtualtable.assign(Query) I can fill my memorytable with fields and
their data from the datacomponent Query.
But TBufdataset doesn't except it. This is my procedure:
Code: [Select]procedure TScreenLevels.LoadScreenTable;
var  Query : TSQLQuery;
begin
  FTableLoaded := true;
  try
    try
      Query               := TSQLQuery.create(nil);
      query.DataBase      := FIBConn;
      Query.Transaction   := FTransaction;
      Query.SQL.Text      := 'SELECT * FROM schermen ORDER BY scherm';
      Query.Active        := true;
      FMemdataset.Assign(Query);
      FMemdataset.Active  := true;
      FMemdataset.IndexFieldNames := 'scherm';
      Query.Active        := false;
    except
      FTableLoaded := false;
    end;
  finally
    Query.free;
  end;
end;
How do I fill Tbufdataset if this is not the right way?

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goodname · 2013-11-14 03:16

Don't know if it is the best method but you could look into streams.

query.SaveToStream();
bufDataSet.LoadFromStream();

The TmemDataset and TBufDataset are different so not sure which your
actually trying to work with.

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LacaK · 2013-11-14 06:06

For TMemDataset you can use: TMemDataset.CopyFromDataset
For TBufDataset you can use: as mentioned by goodname: LoadFromStream
(but only from stream to which was data saved from TBufDataset ot its
descendant like TSQLQuery)

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mangakissa · 2013-11-14 08:01

TMemtable is fixed (lookup problem) in the next release, so it's not
an option.
For using TStream to fill a TBufdataset is a little bit strange, but I
can manage that.

But is TBufdataset not a part of TSQLQuery?

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mangakissa · 2013-11-14 09:15

I Only need the data in memory to read it in several forms. TSQLQuery
derives from TBufDataset, so the dataset is already in memory. no
transaction will be used and when refreshing the dataset, I only have
to call refresh. My solution:
Code: [Select]procedure TScreenLevels.LoadScreenTable;
begin
  try
    FMemdataset.DataBase      := FIBConn;
    FMemdataset.SQL.Text      := 'SELECT * FROM schermen ORDER BY
scherm';
    FMemdataset.PacketRecords := -1;
    FMemdataset.Active        := true;
  except
    FTableLoaded := false;
  end;
end;

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mangakissa · 2016-02-02 21:05

I still need a copy of the dataset into a bufdataset.
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i var
BufStream : TMemoryStream;begin.......SQLQuery.Active := true;SQLQuery
.SaveToStream(BufStream,dfBinary);BufDataset.LoadFromStream(BufStream,
dfBinary);.....end;     But I got a runtime error dataformat is not
reconised when load the stream.

But TMemDataset.CopyFromDataset(dataset,false) did the trick. I only
need to have a clear dataset with the same fields without any
restrictions of required fields.
Now I can append a few records to print some blanc records in my
reportbuilder.

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tatamata · 2016-02-03 07:15

ZMQueryDataset, which is direct TBufDataset descendent, has
CopyFromDataset method.
Plain and simple, you can copy any dataset instantly to ZMQuryDataset.