HEXISTS for field check in Redis - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the Redis command HEXISTS do?

It checks if a specific field exists in a hash stored at a given key. It returns 1 if the field exists, otherwise 0.

beginner

How do you use HEXISTS to check if the field age exists in the hash user:100?

You run the command: HEXISTS user:100 age. It returns 1 if age is a field in the hash, else 0.

beginner

What type of Redis data structure does HEXISTS work with?

It works only with hashes, which are collections of field-value pairs stored under a key.

intermediate

What will HEXISTS return if the key does not exist in Redis?

It returns 0 because the field cannot exist if the hash key itself does not exist.

intermediate

Why is HEXISTS useful in real-life applications?

It helps quickly check if a specific piece of data (field) exists in a hash without retrieving the whole hash, saving time and resources.

What does the Redis command HEXISTS myhash field1 return if field1 exists?

A Error

B 0

C 1

D null

HEXISTS returns 1 if the field exists in the hash.

If the hash key does not exist, what does HEXISTS return?

A 0

B null

C 1

D Error

If the key does not exist, HEXISTS returns 0 because the field cannot exist.

Which Redis data type is required to use HEXISTS?

A Hash

B List

C String

D Set

HEXISTS works only with hashes.

What is the main benefit of using HEXISTS instead of retrieving the whole hash?

A Deletes the field

B Returns the field value

C Adds a new field

D Checks field existence quickly without fetching all data

HEXISTS checks if a field exists without fetching the entire hash, saving time and resources.

Which of these commands is correct to check if field email exists in hash user:1?

A HGET user:1 email

B HEXISTS user:1 email

C HSET user:1 email

D HDEL user:1 email

HEXISTS user:1 email checks if the field email exists.

Explain how the Redis command HEXISTS works and when you would use it.

Think about checking for a specific piece of data inside a collection without loading everything.

Describe what happens if you run HEXISTS on a key that does not exist in Redis.

Consider what it means for a field to exist if the whole hash is missing.