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 Article: Relational Operators in C#
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AskSQLTeam
Ask SQLTeam Question

USA
0 Posts

Posted - 02/04/2004 :  18:17:05  Show Profile  Visit AskSQLTeam's Homepage  Reply with Quote

The SQLTeam Weblogs have been running for a few months now, with some great content. Of particular note is DavidM's series on DataTable Relational Operators in C#. David has written methods in C# to reproduce the relational operators Join, Union, Difference, Divide, Interect, Product, Restrict and TClose using DataTables. The series concludes with an example using the Northwind database.


If you are doing any work with DataTables in .NET this is a must read. Thanks David.


Article Link.

Arnold Fribble
Yak-finder General

United Kingdom
1961 Posts

Posted - 02/10/2004 :  06:52:01  Show Profile  Reply with Quote
I'm lost. What's it for?
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byrmol
Shed Building SQL Farmer

Australia
1591 Posts

Posted - 02/10/2004 :  07:01:23  Show Profile  Reply with Quote
DataSet "relational" operations. .NET's main result set (DataSet) has features that make it appear like an In Memory DBMS. It has "collections" of tables (DataTable), supports Primary Keys, Foreign Key's. The problem is there is no query engine.... The Introduction article gives the reason why I had to write it.

DavidM

"SQL-3 is an abomination.."
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Arnold Fribble
Yak-finder General

United Kingdom
1961 Posts

Posted - 02/10/2004 :  07:30:12  Show Profile  Reply with Quote
Ah, I think I see. Because these DataSets are being sent to clients, it's reasonable to expect them to be small. So writing a set of operators that allow programmers to use a relational style when working with DataSets can be done in a fairly straight-forward way, without worrying about optimization between operators. Is that correct?
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Stoad
Freaky Yak Linguist

*
1983 Posts

Posted - 02/10/2004 :  12:49:29  Show Profile  Visit Stoad's Homepage  Reply with Quote
Not only that.
Just imagine a client that retrieves tabular data
from different, inaccessible to each other, sources.
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byrmol
Shed Building SQL Farmer

Australia
1591 Posts

Posted - 02/10/2004 :  17:24:50  Show Profile  Reply with Quote
That is spot on Arnold. And Stoad's comment is exactly why I had to do it. One set from DB2 and the other SQL Server.... It is with sad regret that I tell you that the middle tier does all the work now and the code has been assigned to the dust bin of source safe.


DavidM

"SQL-3 is an abomination.."
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Merkin
Funky Drop Bear Fearing SQL Dude!

Australia
4970 Posts

Posted - 02/10/2004 :  17:50:22  Show Profile  Visit Merkin's Homepage  Reply with Quote
quote:

code has been assigned to the dust bin of source safe.


Then I hope you made another copy! You never know when SortaSafe is going to eat your code


Damian
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byrmol
Shed Building SQL Farmer

Australia
1591 Posts

Posted - 02/10/2004 :  17:55:31  Show Profile  Reply with Quote
I think every one learns that the hard way Damian.. I have about 6 backups of my code library.

DavidM

"SQL-3 is an abomination.."
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Merkin
Funky Drop Bear Fearing SQL Dude!

Australia
4970 Posts

Posted - 02/10/2004 :  18:03:57  Show Profile  Visit Merkin's Homepage  Reply with Quote
Tell me about it, I just set up FTP backups of my CVS repository. The thought of the backups stored in the same building kept me awake at night



Damian
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