Data.DB.TField.Calculated
| [–] Properties | |
|---|---|
| Type: property | |
| Visibility: public | |
| Source: Data.DB.pas Data.DB.hpp
| |
| Unit: Data.DB | |
| Parent: TField | |
Delphi
property Calculated: Boolean read GetCalculated write SetCalculated default False;
C++
__property bool Calculated = {read=GetCalculated, write=SetCalculated, default=0};
Description
Determines whether the value of the field is calculated by the OnCalcFields event handler of its dataset.
Use Calculated to determine if the field is a calculated field. When Calculated is True and the OnCalcFields event occurs, the OnCalcFields event handler updates the value of the field. The default value is False.
The value of a Calculated field is not stored in or retrieved from the physical tables underlying a dataset. Instead, calculated fields are calculated for each record in the table by the dataset's OnCalcFields event handler, which typically uses expressions involving values from other fields in the record to generate a value for each calculated field.
For example, a dataset might have non-calculated fields for Quantity and UnitPrice, and a calculated field for ExtendedPrice, which would be calculated by multiplying the values of the Quantity and UnitPrice fields in an OnCalcFields event handler.
Note: Do not change the setting of Calculated in application code. Calculated is automatically set to True by the Fields editor at design time if a field's value is specified as calculated.
Note: Do not confuse the Calculated property with the InternalCalcField property of a field definition. The value of a calculated field is computed in the OnCalcFields event handler. The value of an internally calculated field is computed by the SQL server or the Borland Database Engine.