FDCommand: TFDCommand;
..............................
FDCommand.CommandText.Text := 'DO $$ ' + #13#10 +
                  'DECLARE ' + #13#10 +
                  '     val1 integer; ' + #13#10 +
                  '     val2 integer; ' + #13#10 +
                  '     val3 integer; ' + #13#10 +
                  'BEGIN ' + #13#10 +
                  '     val1 := :p_val1; ' + #13#10 +
                  '     val2 := :p_val2; ' + #13#10 +
                  '     val3 := :p_val3; ' + #13#10 +
                  '     INSERT INTO data(value1, value2, value3) ' + #13#10 +
                  '     VALUES(val1, val2, val3); ' + #13#10 +
                  'END; ' + #13#10 +
                  '$$;';
FDCommand.Params.Prepare(ftInteger, ptInput);
FDCommand.Params.ParamByName('p_val1').Value := 0;
FDCommand.Params.ParamByName('p_val2').Value := 0;
FDCommand.Params.ParamByName('p_val3').Value := 0;
FDCommand.Execute();