Ck: Candidate itemset of size kLk : frequent itemset of size kL1 = {frequent items};for (k = 1; Lk !=?; k++) do begin Ck+1 = candidates generated from Lk; for each transaction t in database do increment the count of all candidates in Ck+1 that are contained in t Lk+1 = candidates in Ck+1 with min_support endreturn ?k Lk;SQL应用
Suppose the items in Lk-1 are listed in an orderStep 1: self-joining Lk-1 insert into Ckselect p.item1, p.item2, …, p.itemk-1, q.itemk-1from Lk-1 p, Lk-1 qwhere p.item1=q.item1, …, p.itemk-2=q.itemk-2, p.itemk-1 < q.itemk-1Step 2: pruningforall itemsets c in Ck doforall (k-1)-subsets s of c doif (s is not in Lk-1) then delete c from Ck