SDIFF key1 key2 ... keyN
TIME COMPLEXITY: O(N) with N being the total number of elements of all the sets
DESCRIPTION: Return the members of a set resulting from the difference between the first set provided and all the successive sets. Example:
key1 = x,a,b,c key2 = c key3 = a,d SDIFF key1,key2,key3 => x,b
Non existing keys are considered like empty sets.
RETURN VALUE: Multi bulk reply, specifically the list of common elements.