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Calculated Fields - How to

Posted on 1998-10-27
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Last Modified: 2010-04-06
Simple question. How do I define and access a calculated field in a table.

I have two field values i want to multiply, with the total going in the calculated field.

Thanks.
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Question by:DougBennett
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Expert Comment

by:ZifNab
ID: 1344651
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Accepted Solution

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pc_melsa earned 10 total points
ID: 1344652
To add calculated fields, use the field editor, which is accessed by double clicking the TTable Component. Select the Define button, you'll nee to supply a new field name and the data type of the field.
Delphi 2,3 executes the procedure in the OnCalcFields event handler whenever there is need to recalculated field.
While in the OnCalcFields event handler, the dataset will be in dsCalcFields state.

Here is the example :

procedure MyForm.InventoryCalcFields(Dataset: TDataSet) ;
VAR
   CurrentPrice, LbsPerYard, YardsInStock : double ;
BEGIN
   CurrentPrice := MyTable['CostPerYard'].AsFloat ;
   LbsPerYard   := MyTable['LbsPerYard'].AsFloat ;
   YardsInStock := MyTable['CubicYards'].AsFloat ;

    // Assign value to the fields that are calculated
   MyTable['MarketValue'].AsFloat := CurrentPrice * YardsInStock ;
   MyTable['LbsInStock'].AsFloat := LbsPerYard * YardsInStock ;
END ;


Hope you'll satisfied.
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Expert Comment

by:pc_melsa
ID: 1344653
Thank you very much !
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