SDIFFSTORE destination key [key ...]
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
This command is equal to SDIFF, but instead of returning the resulting set, it
is stored in destination.
If destination already exists, it is overwritten.
Return
Integer reply: the number of elements in the resulting set.