Giao hoán π với ⋈ ( or × )π L( R ⋈ C S)≡(π A1,…,An (R)) ⋈ C (π B1,…,Bm (S))L = { A1,…, An, B1,…, Bm }join condition C only involves LGeneral Formπ L ( R ⋈ C S) ≡π L ((π A1,…A1,…,An, An+
1,…An+
1,…,An+k (R)) ⋈(π19(S))B1,…B1,…,Bm, Bm+
1,…Bm+
1,…,Bm+pHệ quản trị CSDL @ BM HTTTCá[r]