1-select * from b_urunler,b_indirimli_urunler where b_urunler.urun_id=b_indirimli_urunler.urun_id
2- select ad,soyad,cep_tel from b_musteriler 
3- select * from b_urunler where firma_id<=15
4 -select * from b_musteriler where soyad='Yılmaz'