the difference between two queries

Hi. What is the difference between two queries?, that using first one I can get the datas, but using the second one I cannot get the datas.

That's why it does not work:

SqlCommand cmd = new SqlCommand("select  raz_ru_kaz.rus, raz_ru_kaz.kaz from raz_ru_kaz inner join raz_ru_kaz_mavzu on raz_ru_kaz_mavzu.id=raz_ru_kaz.id where raz_ru_kaz_mavzu.rus_mavzu=N'Дробные числительные и проценты'", con);