SADD key member [member …]

Time complexity: O(1) for each element added, so O(N) to add N elements when the command is called with multiple arguments.

Add the specified members to the set stored at . Specified members that are already a member of this set are ignored. If does not exist, a new set is created before adding the specified members.

: the number of elements that were added to the set, not including all the elements already present into the set.

redis> SADD myset "Hello"

redis> SADD myset "World"

redis> SMEMBERS myset