Question

delphi给变量赋值不成功

procedure TForm1.Button1Click(Sender: TObject);
var
S:string;
begin
clientdataset1.Close;
clientdataset1.CommandText:='select pdline_name,t3.serial_number,t1.serial_number SMT_SN,out_process_time from sajet.g_sn_travel t1,sajet.sys_pdline t2,sajet.g_sn_keyparts t3 '
+'where t1.serial_number=t3.item_part_sn and t1.pdline_id=t2.pdline_id and length( item_part_sn) =12 and t1.process_id=''100037'' and '
+'t3.serial_number=:S';
clientdataset1.Params.ParamValues['S']:=trim(edit1.Text);
showmessage(clientdataset1.CommandText);
clientdataset1.Open;

Answer 1

procedure TForm1.Button1Click(Sender: TObject);
var
S:string;
begin
clientdataset1.Close;
clientdataset1.CommandText:='select pdline_name,t3.serial_number,t1.serial_number SMT_SN,out_process_time from sajet.g_sn_travel t1,sajet.sys_pdline t2,sajet.g_sn_keyparts t3 '
+'where t1.serial_number=t3.item_part_sn and t1.pdline_id=t2.pdline_id and length( item_part_sn) =12 and t1.process_id=''100037'' and '
+'t3.serial_number='''+trim(edit1.Text)+'''';
showmessage(clientdataset1.CommandText);
clientdataset1.Open;
这样肯定没有问题，还利于调试

追问

有问题，变量前后加上了双引号

追答

如果serial_number是整数就把引号去掉就可以
我以为serial_number是字符型

Answer 2

针对Params赋值时候，并不会马上体现在SQL语句中，而是在执行SQL的时候将这些参数一起提交给数据库，数据库执行处理这些东西，所以你见到的SQL中参数:S是没变的。通常测试这种SQL是否正确是SQL语句本身是否正确，参数类型及值是否正确

Answer 3

clientdataset1.Params.ParamValues['S']:=trim(edit1.Text);
改成
clientdataset1.ParamByName('S').AsString:=trim(edit1.Text);
试试