TSQLQuery and TCSVDataSet
lazarus / 16-Databases

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egsuh · 2023-04-24 03:53

I checked that SaveToStream and LoadFromStream of TBufDataSet and
TSQLQuery are compatible, as they are not virtual methods. Is there
the same compatibility between TCSVDataSet and TSQLQuery? I cannot
find the hierarchy of TCSVDataSet.

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TRon · 2023-04-24 05:28

Hierarchy as in class hierarchy ? if so then
https://www.freepascal.org/daily/packages/fcl-
db/csvdataset/tcsvdataset.html

TCSVDataset -> TCustomCSVDataset -> TBufDataset -> TCustomBufDataset
-> TDBDataset -> TDataSet -> TObject

It does use other names for the stream/file load/save functions though
(LoadFromCSVStream, LoadFromCSVFile, SaveToCSVStream and
SaveToCSVFile).

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egsuh · 2023-04-24 06:30

QuoteHierarchy as in class hierarchy ? if so then
https://www.freepascal.org/daily/packages/fcl-
db/csvdataset/tcsvdataset.html
Thank you for the information.

You are right.  CSVDataSet1.LoadFromStream(SQLQuery1) does not work. 
But CSVDataSet1.CopyFromDataSet(BufDataSet1) works.

It's really interesting.

When I edited in the BufDataSet, and copy it to SQLQuery and
ApplyUpdates like following, this works.

BufDataSet1.SaveToStream(AStrm);
SQLQuery1.LoadFromStream(AStrm);
SQLQuery1.ApplyUpdates;


In this case, delete, update, or insertions are processed correctly.
Probably the editings done on the TBufDataSet is stored and copied to
TSQLQuery. So I can use the cashed updates with the SQLquery, with
proper InsertSQL, etc.

I expected this works without any definition of InsertSQL, DeleteSQL,
or UpdateSQL using IndexFields, but it does not seem to work.

Once I make CopyFromDataSet, this functionality goes away --- but I
can delete all pre-existing records and call ApplyUpdate, only with
InsertSQL.