HKEYS and HVALS in Redis - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What does HKEYS return?

Given a Redis hash stored as HSET user:1 name "Alice" age "30" city "Paris", what is the output of HKEYS user:1?

Redis

HSET user:1 name "Alice" age "30" city "Paris"
HKEYS user:1

A ["name", "age", "city"]

B ["Alice", "30", "Paris"]

C ["user:1"]

D []

💡 Hint

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

The HKEYS command returns a list of all the field names (keys) stored inside the hash. It does not return the values or the hash key itself.

❓ query_result

intermediate

What does HVALS return?

Given a Redis hash stored as HSET product:100 price "19.99" stock "50" category "books", what is the output of HVALS product:100?

Redis

HSET product:100 price "19.99" stock "50" category "books"
HVALS product:100

A ["19.99", "50", "books"]

B ["price", "stock", "category"]

C ["product:100"]

D []

💡 Hint

HVALS returns all the values inside the hash fields.

The HVALS command returns a list of all the values stored inside the hash fields. It does not return the field names or the hash key.

🧠 Conceptual

advanced

Difference between HKEYS and HVALS

Which statement correctly describes the difference between HKEYS and HVALS in Redis?

A <code>HKEYS</code> returns all keys in Redis; <code>HVALS</code> returns all values in Redis.

B <code>HKEYS</code> returns all field values; <code>HVALS</code> returns all field names.

C <code>HKEYS</code> returns all field names; <code>HVALS</code> returns all field values.

D <code>HKEYS</code> returns the hash key; <code>HVALS</code> returns the hash size.

💡 Hint

Think about what each command returns from inside the hash.

HKEYS returns the field names (keys) inside a hash, while HVALS returns the values of those fields. They do not return the hash key or all keys in Redis.

📝 Syntax

advanced

Identify the syntax error

Which of the following Redis commands will cause a syntax error?

A HVALS product:100

B HKEYS

C HKEYS user:1

D HVALS orders:2023

💡 Hint

Check if the command has the required arguments.

Both HKEYS and HVALS require a key argument. Option B misses the key, causing a syntax error.

❓ optimization

expert

Efficiently retrieving all fields and values

You want to retrieve all fields and their values from a large Redis hash named session:123. Which command is the most efficient to get both keys and values in one call?

A HKEYS session:123

B HVALS session:123

C HMGET session:123 *

D HGETALL session:123

💡 Hint

Think about a command that returns both keys and values together.

HGETALL returns all fields and their values in one call. HKEYS and HVALS return only keys or values separately. HMGET requires specific fields, not a wildcard.