Index Nested Loops Join
•If there is an index on the join column of one relation (say S), can make it the inner.
–Cost:  M + ( (M*pR) * cost of finding matching S tuples)
•For each R tuple, cost of probing S index is about 1.2 for hash index, 2-4 for B+ tree.  Cost of then finding S tuples depends on clustering.
–Clustered index:  1 I/O (typical), unclustered: up to 1 I/O per matching S tuple.
foreach tuple r in R do
foreach tuple s in S where ri == sj  do
add <r, s> to result