What is the difference between the MasterSource and DataSource
properties?
lazarus / 16-Databases

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vfclists · 2013-06-01 05:28

What is the difference between the MasterSource and DataSource
properties of a dataset?

From what I understand and know from experience the DataSource points
to the master source table in a master->detail link. The MasterSource
also seems to do the same thing. Why the duplication?

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taazz · 2013-06-01 09:23

As far as I can see on lazarus 1.0.6 and fpc 2.6.2 the MasterSource
does not exists on the TDataset or TSQLQuery from the SQLDB
components, which dataset you use that has masterSource?

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jamhitz · 2013-06-01 12:14

Datasource provides a link to the underlying database table. Where
available, the MasterSource points to ANOTHER TDataSet descendant that
provides the MASTER half of a MASTER-DETAIL relationship through the
MasterFields property.

Used to employ this back in the day using Delphi. Zeos still has it,
but sqlDB does not seem to employ it.

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vfclists · 2013-06-01 16:39

It is present in the Zeos package. Anyway further investigation
indicates that MasterSource is used with the TTable based
master->detail linking which created the links by matching field names
in the master with the corresponding fields in the detail.

The DataSource property is SQL based and it creates the link by using
the Params property of the SQL where fields in the detail query
prefixed with ':'  match the corresponding fields in the master query.

Code: [Select]select * from detail where detail.master_id = :master_id

Quote from: taazz on June 01, 2013, 11:23:04 amAs far as I can see on
lazarus 1.0.6 and fpc 2.6.2 the MasterSource does not exists on the
TDataset or TSQLQuery from the SQLDB components, which dataset you use
that has masterSource?