[SYMBOL] [A] [B] [C] [D] [E] [F] [G] [H] [I] [J] [K] [L] [M] [N] [O] [P] [Q] [R] [S] [T] [U] [V] [W] [X] keys entity keys 2nd Foreign Keys foreign keys Foreign Keys domain integrity Primary Keys 2nd 3rd 4th primary keys Primary Keys as clustered indexes surrogate keys KEYSET 2nd keywords DISTINCT 2nd 3rd |