April 2003
Beginner to intermediate
620 pages
21h 48m
English
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Merging Two DataSets
The Merge( )
method
combines the data and structure of a second, or source,
DataSet into a specified target
DataSet with a similar structure. The
Merge( ) method is typically used in a client
application to update a DataSet with the latest
changes to the underlying data in the data source.
When the Merge( ) method is called, the schemas of
the source and target DataSet are compared. If
there are schema differences, the
MissingSchemaAction argument determines whether
the target schema is updated to include the missing schema and data
or whether an exception is raised. If the
MissingSchemaAction is specified as
Add or AddWithKey, the schema
is extended to accommodate the new data, and the primary key
information added in the case of the later value. Specifying
Ignore results in the data for the missing schema
being ignored; specifying Error results in an
exception being raised.
During the merge operation, source rows with a
RowState of Unchanged,
Modified, or Deleted are
matched to rows in the target DataSet with the
same Current primary key values. Source rows with
RowState of New are created in
the target DataSet with the same primary key
values as the Current value in the source because
the Original version doesn’t
exist in the source. Figure 6-2 shows the result of
merging two tables with similar schemas, accepting the default
MissingSchemaAction value of
Add.
Figure 6-2. Merging DataSet objects
If the optional PreserveChanges argument is set to
true, incoming ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.