 Usage:

ZUNION numkeys key [ key ... ] [ WEIGHTS weight ] [ [ WEIGHTS weight ] ... ] [ AGGREGATE sum  min  max ] [ withscores ]
 Complexity:
 O(N)+O(M*log(M)) with N being the sum of the sizes of the input sorted sets, and M being the number of elements in the resulting sorted set.
 Since:
 6.2.0
This command is similar to ZUNIONSTORE
, but instead of storing the resulting
sorted set, it is returned to the client.
For a description of the WEIGHTS
and AGGREGATE
options, see ZUNIONSTORE
.
Examples
127.0.0.1:6379> ZADD zset1 1 "one"
(integer) 1
127.0.0.1:6379> ZADD zset1 2 "two"
(integer) 1
127.0.0.1:6379> ZADD zset2 1 "one"
(integer) 1
127.0.0.1:6379> ZADD zset2 2 "two"
(integer) 1
127.0.0.1:6379> ZADD zset2 3 "three"
(integer) 1
127.0.0.1:6379> ZUNION 2 zset1 zset2
1) "one"
2) "three"
3) "two"
127.0.0.1:6379> ZUNION 2 zset1 zset2 WITHSCORES
1) "one"
2) "2"
3) "three"
4) "3"
5) "two"
6) "4"