ZUNIONSTORE

    Computes the union of sorted sets given by the specified keys, and stores the result in destination. It is mandatory to provide the number of input keys (numkeys) before passing the input keys and the other (optional) arguments.

    Using the WEIGHTS option, it is possible to specify a multiplication factor for each input sorted set. This means that the score of every element in every input sorted set is multiplied by this factor before being passed to the aggregation function. When WEIGHTS is not given, the multiplication factors default to 1.

    If already exists, it is overwritten.

    1. dragonfly> ZADD zset1 1 "one"
    2. (integer) 1
    3. dragonfly> ZADD zset1 2 "two"
    4. dragonfly> ZADD zset2 1 "one"
    5. (integer) 1
    6. dragonfly> ZADD zset2 2 "two"
    7. (integer) 1
    9. (integer) 1
    10. (integer) 3
    11. dragonfly> ZRANGE out 0 -1 WITHSCORES
    12. 1) "one"
    13. 2) "5"
    14. 3) "three"
    15. 4) "9"