Queries against a dataset

  • Thread starter Thread starter Tobe
  • Start date Start date
T

Tobe

Is there anyway to run a query against a dataset in
ADO.NET? For example, I have two tables already in a
dataset, is there anyway to do a join on those two tables
and get a resulting table?

This would be especially useful for:
1. tables in two different databases, or
2. joins on tables already in memory without hitting the
database again.
 
Convert to XML and manipulate, or write another query to return another
table in your DataSet. There is no way, currently, to make a view across two
DataTables. You can filter the results, with a DataView, but only on one
table.

I would imagine this functionality will rear its head in the future, as many
people are asking for it.

--
Gregory A. Beamer
MVP; MCP: +I, SE, SD, DBA
Author: ADO.NET and XML: ASP.NET on the Edge

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Think Outside the Box!
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Is there anyway to run a query against a dataset in
ADO.NET? For example, I have two tables already in a
dataset, is there anyway to do a join on those two tables
and get a resulting table?

This would be especially useful for:
1. tables in two different databases, or
2. joins on tables already in memory without hitting the
database again.
Click to expand...

Dear Tobe

To begin with I found it difficult not to think of a dataset as a mini
database and, therefore, that I should be able write SQL queries. But
it ain't so I can't.

Under *some* circumstances you might find that data table columns
defined as expressions are a solution. A "child" row can refer to its
parent's columns (e.g. a row with, say, an "account number" foreign
key can display the corresponding "account name"). Similarly, a
"parent" row can display aggregated results (sum, avg etc) from its
child rows. Expression type columns can be included in strongly typed
data sets - if you use them.


Another possibility is the use of a helper class to (sort of) emulate
a SQL Query with a join.

Here's a, potentially, useful reference...

http://support.microsoft.com/default.aspx?scid=kb;en-us;326080


Regards

Neil Allen
 
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