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CodeRage 9 Q&A: NestedDataSets in ClientDataSets (Cary Jensen)

Posted by jpluimers on 2014/10/30

Session:

NestedDataSets in ClientDataSets

A column of a ClientDataSet can contain a dataset, a tabular structure containing one or more columns and zero or more records. This presentation continues Cary Jensen’s CodeRage series on ClientDataSets by looking at this power field type.

Level: All
Cary Jensen – Jensen Data Systems, Inc.

Q&A:

Audience Question

  • Q: Would nested datasets akso be usable for defining new, lacking records in different tables
  • A: Yes. In the presentation I demonstrate creating nested dataset structures where no underlying database already exists

Audience Question

  • Q: Would nested datasets be something similar to a view made from lot of tables with ‘from table1 left join t on (table2.key=table1.key) left join …………
  • A: No. That would create a single table with values from two tables. A nested dataset is a dataset nested within a field of another dataset. With nested datasets you actually have two or more different tables

Audience Question

  • Q: Is there an easy way to exncrypt the data in a file that was written out using clientdataset or FDMemTable to for instance XML or JSON type file? Would one need to stream it and then encrypt/decrypt the stream upon writing/reading?
  • A: You got it right in you suggestion. To encrypt, you write from the CDS or FDMemTable to a stream, encrypt the stream, and then write that stream. You do the same in reverse to load the encrypted data

Audience Question

  • Q: ClientDataSet can be connected to 3rd party datasets using the provider component.Is FDMemtable limited to Firedac datasets ?
  • A: FDMemTables are currently designed for FireDAC datasets

Audience Question

  • Q: If I have a many to many relationship using an intersection table in between (Table A 1-n Table AB n-1 Table B). How do I write this out using the nested datasets?
  • A: To a file, call SaveToFile on the top-level CDS

Audience Question

  • Q: How am I going to get you to sign your new book !!! Having got you to sign your back back in London Delphi Deve Days !! LOL
  • A: We’ll just have to get you back to a Delphi Developer Days :)

Audience Question

  • Q: Nice presentation Carry
  • A: Thank you

Audience Question

Audience Question

  • Q: You show both the MidLevelCDS and the ThirdLevelCDS owned by the TopLevelCDS. Would/should the ThirdLevelCDS be owned by the MidLevelCDS instead?
  • A: The ownership is a detail, and has no effect on the master-detail linkage

Audience Question

  • Q: Audio: Still some artifacts, but clearer than it was
  • A: :-)

Audience Question

  • Q: I am routinely impressed with Cary’s knowledge and communication skills. Both contribute to my enthusiasm for Object Pascal! THANKS
  • A: :-)

Audience Question

  • Q: Great Presentation! I used this technique in a moblie application. It takes a little longer to load, initially, but once the data is loaded, no more round trips are required – which makes the app MUCH more robust.
  • A: :-)

Audience Question

  • Q: I was thinking about an a customer exists, but a certain order is lacking, could that lacking order record be inserted?
  • A: Not only can it be inserted into the detail table nested dataset, that record will be inserted by the TLD by a call to ApplyUpdates.

Audience Question

Audience Question

  • Q: An example on this compressing/encypting/saving and then loading/decrypting/uncompressing would be great.
  • A: Yes it would. Thanks.

Audience Question

  • Q: where do you find the latest version of the Turbo Power stuff
  • A: Source Forge

Audience Question

  • Q: Great Presentation! I used this technique in a moblie application. It takes a little longer to load, initially, but once the data is loaded, no more round trips are required – which makes the app MUCH more robust.
  • A: http://blog.kassebaum.eu/?p=379

Audience Question

  • Q: Is there a possibility in future that tclientdataset becames deprecated?
  • A: I doublt it, at least not anytime in the near future

Audience Question

  • Q: There are multiple flavors on SourceForge (…”New”)
  • A: Great.

More information on the special offers http://www.embarcadero.com/radoffer

Audience Question

Audience Question

  • Q: Confirmed – The link works
  • A: :-)

Audience Question

  • Q: Hope systools also would be part of the pacoage
  • A: That one might get some attention later. ;-)

–jeroen

via: CodeRage 9 – Object Pascal Sessions.

One Response to “CodeRage 9 Q&A: NestedDataSets in ClientDataSets (Cary Jensen)”

  1. […] CodeRage 9 Q&A: NestedDataSets in ClientDataSets (Cary Jensen) […]

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