In Redis, hash tables allow for efficient storage of data as structures that represent associative arrays or objects, making them ideal for storing objects with multiple fields.

Redis itself can be considered a hash table since it has string keys and corresponding values, which can be of various data types.

Key Commands for Working with Hash Tables

Redis provides several commands for working with hash tables, which can be grouped based on their purpose: for setting, getting, and manipulating data within hashes.

To begin with, to set or update values in a hash, use the HSET command:

HSET user:1000 name "Alice"

This command adds or updates the name field in the hash with the key user:1000. To retrieve the value of a field, use the HGET command:

HGET user:1000 name

It returns the value of the name field from the user:1000 hash. If you need to work with multiple fields, use HGETALL to get all key-value pairs from the hash:

HGETALL user:1000

This will return all fields and their values from the hash. You can also retrieve only the values of the fields using HVALS, or to get only the keys, use the HKEYS command:

HVALS user:1000
HKEYS user:1000

When you need to delete one or more fields from a hash, use the HDEL command:

HDEL user:1000 name

This deletes the name field from the user:1000 hash. After deleting a field, if you need to check whether a specific field exists, use the HEXISTS command:

HEXISTS user:1000 name

It returns 1 if the field exists, and 0 if it doesn't. If you need to change a numeric field (for example, incrementing its value), use the HINCRBY command:

HINCRBY user:1000 age 1

This command increments the age field by 1. Finally, to get the number of fields in a hash, use the HLEN command:

HLEN user:1000

This will return the number of fields in the user:1000 hash.