ZADD

Synopsis

ZADD key [NX|XX] [CH] [INCR] score member [score member ...]
This command sets all specified members with their respective scores in the sorted set specified by key, with multiple score member pairs possible. If a specified member is already in the sorted set, this command updates that member with the new score. If the key does not exist, a new sorted set is created, with the specified pairs as the only elements in the set. A score should be a double, while a member can be any string.

Return value

The number of new members added to the sorted set, unless the CH option is specified (see below).

ZADD options

XX: Only update `members` that already exist. Do not add new `members`.

NX: Do not update `members` that already exist. Only addd new `members`.

CH: Modify the return value from new `members` added to `members` added or updated.

INCR: Increment the specified `member` by `score`. Only one `score` `member` pair can be specified.

Examples

Add two elements into the sorted set.

(integer) 2

Update an element in the set. Note the return value is 0, since you do not add a new member.

(integer) 0

Now you add a new member with an existing score. This is fine, since multiple members can have the same score.

(integer) 1

Now, see the members in the sorted set. Note the sort order by score. Since both v1 and v3 have the same score, you use comparison on the members themselves to determine order.

1) "v2"
2) "2.0"
3) "v1"
4) "3.0"
5) "v3"
6) "3.0"

With the XX option specified, only update exiting members. Here, only v1 is modified.

(integer) 0

With the NX option specified, only add new members. Here only v4 is added.

(integer) 1

With the CH option specified, return number of new and updated members.

(integer) 2

With the INCR option specified, increment by score. Score of v5 should now be 6.0.

Let us now see the updated sorted set.

1) "v1"
2) "0.0"
3) "v2"
4) "2.0"
5) "v3"
6) "3.0"
7) "v4"
8) "4.0"
9) "v5"
10) "6.0"

See also

zcard, zrange, zrangebyscore, zrem, zrevrange