delphi中写SQL语句中变量的注意事项

1、procedure TForm1.btn1Click(Sender: TObject);

var

  s: String;

begin

  S := 'select * from TMarketInfo where NO='''+'1''';

  ShowMessage(s);

end;

 

结果显示：select * from  TMarketInfo where NO='1'

 

2、procedure TForm1.btn1Click(Sender: TObject);

var

  s: String;

begin

  S := 'select * from TMarketInfo where NO='+'''1''';

  ShowMessage(s);

end;

结果显示：select * from  TMarketInfo where NO='1'

 

3、procedure TForm1.btn1Click(Sender: TObject);

var

  s: String;

begin

  S := 'select * from TMarketInfo where NO=''+1''';

  ShowMessage(s);

end;

结果显示：select * from  TMarketInfo where NO='+1'

 

4、procedure TForm1.btn1Click(Sender: TObject);

var

  s: String;

begin

  S := 'select * from TMarketInfo where NO='+'1';

  ShowMessage(s);

end;

结果显示：select * from  TMarketInfo where NO=1