If you get an error that reads “WRONGTYPE Operation against a key holding the wrong kind of value” when using the SMEMBERS command in Redis, it’s probably because you’re passing a key with the wrong data type to the command.
The SMEMBERS command is a “set” command, and so it is intended to be used on keys that contain a set. If the key holds a different data type, you’ll likely get the above error.
The Redis HGETALL command returns all fields and values from the hash at the specified key.
The Redis HMGET command allows us to get multiple values from a hash. It returns the value/s associated with the specified field/s in the hash at the specified key.
The Redis HGET command allows us to get a value from a hash. It returns the value associated with the specified field in the hash at the specified key.
The Redis HRANDFIELD command allows us to get a random field from a given key.
The command accepts several arguments that allows us to specify the number of random fields returned, whether to include the same field multiple times, and whether or not to include the values with each field returned.
The HRANDFIELD command was introduced in Redis 6.2.0.
In Redis, the HEXISTS command allows us to check whether a field exists in a given hash. We pass the name of the key and the field to the command, and it returns 1 if the field exists, and 0 if it doesn’t.
If you’re getting an error that reads “ERR numkeys should be greater than 0” in Redis, it’s probably because you’re specifying a wrong value for the first argument when calling the SINTERCARD command.
To fix this issue, make sure you’re passing a valid non-zero value that matches the number of keys you’re comparing.
Continue readingThe Redis HKEYS command returns all fields in the hash stored at the specified key.
In Redis, the HDEL command enables us to delete one or more fields in a hash. It deletes the specified field/s at the specified key.
If the field doesn’t exist, it’s ignored. If the key doesn’t exist, it’s treated as an empty hash and 0 is returned.
In Redis, the HSETNX command enables us to set a field in a hash, but only if the field doesn’t already exist. It sets the field at the specified key to the value we provide.
If the key doesn’t exist, it’s created with the specified hash value. If the field already exists, nothing is set (i.e. the command has no effect).
Continue reading