Add one or more items/members to a set. Multiple member elements are supported in the command. So we can add one or more members to the same set at the same time. If the key does not exist, then it is created and then members are added to it. If the item/member element already exists in the set, then it is ignored.
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Increment the integer value of a hash field. This command increments the field value by a certain amount that is provided. If the hash does not exist, or the field does not exist, then the hash and/or the field will be created. So we will never get any error related to non-existing hash key or field. The field’s max and min allowed value is of a 64-bit signed integer.
Get all the values of a hash. Only the values are returned as a list. To get the keys we can use the HKEYS command. We can use the HGETALL command to get all the keys and values.
Get the list of all fields of a hash. All the items returned, are unique as the field names are unique in a hash. If the key does not exist then we get (empty array) in response, which represents an empty array when used in any programming language.
Get all the fields and values of a hash. By only providing the key of the hash we get all the fields and values. We do not need to be aware of specific field(s). The response contains the field and value of the field in 2 separate lines.
Get the value of a single field of a hash. This is the simplest command for getting the value from a hash, but only one field can be fetched from the hash. HMGET supports multiple fields, and HGETALL returns all data of a hash. So you can use these if these commands serve your purpose.
Create a new hash and set fields, or change the existing value of field(s) of a hash. If the key does not exist then it will be created. If the field does not exist then it will be created. And if the field exists then the value will be overwritten.
Restore data from a serialized(by DUMP command) data. This command creates a key, unserializes the provided data, then stores the value for the key. The expiration time of the original key is not contained in the data, so that is not contained in the created key. RDB version and data checksum are checked before restoring data.
