Sets field in the hash stored at key to value, only if field does not
yet exist.
If key does not exist, a new key holding a hash is created.
If field already exists, this operation has no effect.
*Return value
Integer reply, specifically:
1iffieldis a new field in the hash andvaluewas set.0iffieldalready exists in the hash and no operation was performed.
*Examples
redis>
HSETNX myhash field "Hello"
(integer) 1redis> HSETNX myhash field "World"
(integer) 0redis> HGET myhash field
"Hello"