Changing data type between Provider and Clientdataset

Posted on 2013-01-31
Last Modified: 2013-02-01
I have a stored procedure (sp_who2) that is returning a varchar containing a number (CPUTime).  I am pulling the dataset into a ClientDataSet for use in my program, but would like the column to be an integer so that indexing on it will be in the correct order.  

How can I best do that?
Question by:GNiessen
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LVL 37

Expert Comment

by:Geert Gruwez
ID: 38841414
you mean sorting, not indexing ?
LVL 26

Expert Comment

by:Sinisa Vuk
ID: 38841587
You can do this on server side by casting filed:

select cast(CPUTime as int) as CPUTime, Field2, Field3 from table1....

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Author Comment

ID: 38841714
#Geert  The ClientDataSet has Indexes for sorting.

#sinesav  You can't select from a stored procedure.  If it were a view or a table it would be easy.  And as this is a system stored procedure I can't modify it to run the way I want.
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LVL 37

Expert Comment

by:Geert Gruwez
ID: 38842724
you could  (or ask to) add a sql zone to your Q with request attention

have you tried with a wrapper procedure ?
create a procedure which puts the output of the system proc in a temp table,
then run your select from that temp table

it's been over a decade since i did mssql but here goes ...

if you put a select statement last in your proc it will behave as a query in delphi
LVL 26

Accepted Solution

Sinisa Vuk earned 250 total points
ID: 38842955
I missed "stored procedure". You cannot change field type on the fly because it allocate memory as string. But...

1. add all field defs + one additional 'ID' field defined as Integer and must be InternalCalc of kind.

2. Add procedure SortCustomClientDataSet from page: ... and add following code with new OnCalcField event on dataset (where you convert string to integer on the fly):

procedure TForm1.Button1Click(Sender: TObject);
  SortCustomClientDataSet(ClientDataSet1, 'ID');

procedure TForm1.ClientDataSet1CalcFields(DataSet: TDataSet);
  ClientDataSet1.FieldByName('ID').AsInteger :=
    StrToIntDef(ClientDataSet1.FieldByName('CPUTime').AsString, 0);

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Author Closing Comment

ID: 38843325
Setting up the an internal calc field worked and I was able to index on it.  I had hoped there was a way to control more the data transformation between the stored procedure and the Clientdataset, but it is working good enough for this purpose.

Thanks all.

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