我想把dbcombox里的单击选取项目时激发查询,代码如下,可是只能查询一次,在选取时则无任何相应,哪里错了? procedure TF_rending.DBComboBox4Change(Sender: TObject); begin inherited; with datamodule4 do begin query4.close ; Query4.SQL.Clear; Query4.SQL.Add('select * from ENREGISTER as ss where ss."name"=:name'); Query4.Prepare; Query4.Params[0].AsString:=DBComboBox4.Text; Query4.Open; datasource1.DataSet:=Query4; end; end;