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Delphi字符串使用单引号,例如' a valid string'.如何'在文字字符串中指定字符？如何引用空字节(Unicode代码点U+0000)？

我得到一个ORA-00907:从下面的代码中缺少右括号

 dbQuery:= TQuery.Create(nil);
 dbQuery.DatabaseName:= dbMain.DatabaseName;
 with dbQuery do
 begin
   SQL.Add('select payee_address_zip, EXTRACT(WEEKDAY FROM check_date) as DOW, ');
   SQL.Add('(cmcl_bank_cleared - check_date) as DateDiff from AP_Master ');
   SQL.Add('where (cmcl_bank_cleared is not null) AND ((cmcl_bank_cleared - check_date) >=:DaysParam)');
   SQL.Add('order by payee_address_zip, DOW, DateDiff');
  try
   ParamByName('DaysParam').AsInteger:= days_param_int;
   Open;
   //do something else here      
  except on E:EDatabaseError do
   begin
    raise ECustomException.create('Error opening query for step 1 of computing Float Factors!');
   end;//except
  end; //try
 end; //with
 dbQuery.Free;

有人能告诉我发生了什么事吗？我似乎无法看到我遗漏了一个括号,这个SQL对Interbase测试数据库工作得很好.但是,当它移动到客户端oracle数据库时,它崩溃,上面的错误.