SDIFFSTORE
Stores the members of the set resulting from the difference between the first set and all the successive sets.
Syntax
SDIFFSTORE destination key [key ...]
Details
- Available since: 1.0.0
 - Time complexity: O(N) where N is the total number of elements in all given sets.
 - ACL categories: 
@write,@set,@slow 
Example
Assume we have three sets: set1, set2, and set3 with the following members:
SADD set1 "a" "b" "c"
SADD set2 "b" "c" "d"
SADD set3 "c" "d" "e"
Now, let's store the difference between set1 and set2 in a new set called diff_set:
SDIFFSTORE diff_set set1 set2
RESP2/RESP3 Reply
Integer reply: the number of elements in the resulting set.