Calling the SetParams Method
Go Up to Executing Update Statements
The SetParams method for an update component uses special parameter substitution rules to substitute old and new field values into the update SQL statement. Ordinarily, SetParams is called automatically by the update component’s Apply method. If you call Apply directly in an OnUpdateRecord event, do not call SetParams yourself. If you execute an update object using its ExecSQL method, call SetParams to bind values to the update statement’s parameters.
SetParams sets the parameters of the SQL statement indicated by the UpdateKind parameter. Only those parameters that use a special naming convention automatically have a value assigned. If the parameter has the same name as a field or the same name as a field prefixed with “OLD_” the parameter is automatically a value. Parameters named in other ways must be manually assigned values. For more information see the section Understanding Parameter Substitution in Update SQL Statements.
The following example illustrates one such use of SetParams:
procedure TForm1.EmpAuditUpdateRecord(DataSet: TDataSet;
UpdateKind: TUpdateKind; var UpdateAction: TUpdateAction);
begin
with DataSet.UpdateObject as TIBUpdateSQL do begin
SetParams(UpdateKind);
if UpdateKind = ukModified then
IBQuery[UpdateKind].ParamByName('DateChanged').Value := Now;
ExecSQL(UpdateKind);
end;
UpdateAction := uaApplied;
end;
This example assumes that the ModifySQL property for the update component is as follows:
UPDATE EmpAudit SET EmpNo = :EmpNo, Salary = :Salary, Changed = :DateChanged WHERE EmpNo = :OLD_EmpNo
In this example, the call to SetParams supplies values to the EmpNo and Salary parameters. The DateChanged parameter is not set because the name does not match the name of a field in the dataset, so the next line of code sets this value explicitly.