Re: DataTable.Compute or .Select to count distinct values in a column

[Miha Markic [MVP C#]]

Hi,

I would go with a simple foreach (DataRow row in table.Rows) loop.

 

[Sasidhar]

Miha,
May be I am not getting you. How can you do that using a foreach? Can you
please explain.

MK,
Look at this article. You can utilise it to find out the count.
http://support.microsoft.com/default.aspx?scid=kb;EN-US;326176

Or if the number of rows is less then you can use a for loop and a
hashtable. As you loop insert into hashtable. If you find a duplicate ignore
the key. At the end you can just get the count from hashtable.

-SP

Hi,

I would go with a simple foreach (DataRow row in table.Rows) loop.

--
Miha Markic [MVP C#] - RightHand .NET consulting & development
miha at rthand com
www.rthand.com

I have a Datatable in a DataSet that for one part of the process I need to
know the count of DISTINCT/UNIQUE values in one column. How can I achieve
this.

 

[Miha Markic [MVP C#]]

Hi,

Miha,
May be I am not getting you. How can you do that using a foreach? Can you
please explain.

Well, yes, doing it manually was what i was thinking.
Storing unique value and its count (if you want to count the key occurences
also) in a hashtable is a good one.

--
Miha Markic [MVP C#] - RightHand .NET consulting & development
miha at rthand com
www.rthand.com

MK,
Look at this article. You can utilise it to find out the count.
http://support.microsoft.com/default.aspx?scid=kb;EN-US;326176

Or if the number of rows is less then you can use a for loop and a
hashtable. As you loop insert into hashtable. If you find a duplicate
ignore
the key. At the end you can just get the count from hashtable.

-SP

Hi,

I would go with a simple foreach (DataRow row in table.Rows) loop.

--
Miha Markic [MVP C#] - RightHand .NET consulting & development
miha at rthand com
www.rthand.com

I have a Datatable in a DataSet that for one part of the process I need to
know the count of DISTINCT/UNIQUE values in one column. How can I achieve
this.

 

[Guest]

What I would want is a count of how many different values there are. I could
dump to a hash table, then get the .length. Seems costly...

 

[Steven Cheng[MSFT]]

Hi Mark,

The .net framework's DataTable's select method only provide some very basic
semantics, which haven't include the "unique item count" function, you can
check all the supported semantics in the following link:

#DataColumn.Expression Property
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/
frlrfsystemdatadatacolumnclassexpressiontopic.asp

If you do want to do the unique item query, I think you should consider
other members suggestion that manually loop through the items and count the
distinct ones.


Regards,

Steven Cheng
Microsoft Online Support

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