Simple Nested Loops Join
•For each tuple in the outer relation R, we scan the entire inner relation S.
–Cost:  M +  (pR * M) * N  =  1000 + 100*1000*500  I/Os:  140 hours!
•Page-oriented Nested Loops join:  For each page of R, get each page of S, and write out matching pairs of tuples <r, s>, where r is in R-page and S is in S-page.
–Cost:  M + M*N = 1000 + 1000*500 (1.4 hours)
For each tuple r in R do
for each tuple s in S do
if ri == sj  then add <r, s> to result