Book claims that below query translates to relational algebra expression $P/Q$. Can anyone explain how does the below query translates to relational algebra expression $P/Q$?
Assume $Q$ has attributes $B_1,B_2,...,B_m$ and that $P$ has in addition the attributes $A_1,A_2,...,A_n$.
How above query equates to relation algebra expression $P/Q$?