Ddfhfdffhfdffhfdcfcfcjkncfdkdfkddskwownjdekjcfnnfgnjncncfd
Hdhddduedhedbdgdxyhdhdhdhdjdddxj
Operatia uniunea are doua proprietati. Ea e comutativa, adica r U s = s U r. Ea este si asociativa, adics (r U s) U q = rU(s U q) pentru relaiile mutual compatibile r, s si q. Intersectia a doua relatii compatibile r(R)
Ljhfdsgfsaiufjhef8iwehfsdfcsdhvid
SQL operatii
Shbhddrdfbffddfbfdjfdndfjdfrfdrnfrfirfdnfnfgngjggjgngfdfdf