HKEYS and HVALS in Redis - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the Redis command HKEYS do?

The HKEYS command returns all the field names (keys) stored in a hash at a given key.

beginner

What does the Redis command HVALS do?

The HVALS command returns all the values stored in a hash at a given key.

beginner

If a Redis hash has fields name, age, and city, what will HKEYS return?

It will return a list of the field names: ["name", "age", "city"].

beginner

If a Redis hash has values "Alice", 30, and "NYC" for fields name, age, and city, what will HVALS return?

It will return a list of the values: ["Alice", "30", "NYC"].

intermediate

Can HKEYS and HVALS be used on a Redis key that is not a hash?

No, both commands only work on keys holding hashes. Using them on other data types will cause an error.

What does the Redis command HKEYS myhash return?

A The number of fields in <code>myhash</code>

B All field names in the hash stored at <code>myhash</code>

C All values in the hash stored at <code>myhash</code>

D Deletes the hash <code>myhash</code>

HKEYS returns all the field names (keys) in the hash.

What will HVALS myhash return if myhash has fields name and age with values "Bob" and 25?

A 25

B ["name", "age"]

C ["Bob", "25"]

D An error

HVALS returns all values in the hash.

What happens if you run HKEYS on a Redis string key?

A Returns all characters in the string

B Deletes the string

C Returns an empty list

D Returns an error

Using HKEYS on a non-hash key causes an error.

Which Redis command would you use to get all the values from a hash?

A HVALS

B HKEYS

C HGETALL

D HMGET

HVALS returns all values from a hash.

If a hash is empty, what does HKEYS return?

A Empty list

B List with one empty string

C Error

D Null

HKEYS returns an empty list if the hash has no fields.

Explain what the Redis commands HKEYS and HVALS do and when you would use them.

Think about how you get all keys or all values from a dictionary in programming.

Describe what happens if you use HKEYS or HVALS on a Redis key that is not a hash.

Consider the data type restrictions of Redis commands.