Master Redis: Essential Commands for Strings, Lists, Sets, Sorted Sets, and Hashes

Redis String Commands

Common commands for manipulating simple key‑value pairs:

set      key value          # Set a key‑value pair
get      key                # Retrieve the value of a key
incr     key                # Increment an integer value by 1
decr     key                # Decrement an integer value by 1
strlen   key                # Get the length of a string value
incrby   key increment      # Increment by a specific integer

When the stored value is numeric, Redis treats it as an integer and supports incr, decr, incrby, and decrby operations.

String Application Scenarios

Counters – e.g., page views, likes, inventory counts (atomic because Redis processes commands single‑threaded).

Shared session storage in distributed systems.

Distributed locks using SET key value NX to ensure the key is set only when absent.

Redis List Commands

Lists are ordered collections of strings.

lpush    key v1 v2 …        # Push elements to the left (head)
rpush    key v1 v2 …        # Push elements to the right (tail)
lrange   key start stop    # Retrieve a range of elements
lpop     key                # Pop element from the left
rpop     key                # Pop element from the right
lindex   key index          # Get element by index
llen     key                # Get list length
lrem     key count value    # Remove occurrences of a value
ltrim    key start stop    # Trim list to the specified range
rpoplpush source dest      # Pop from source right and push to destination left
lset     key index value    # Set element at a specific index
linsert  key BEFORE|AFTER pivot value # Insert before or after a pivot element

Internally, Redis uses a quicklist (a hybrid of ziplist and linked list) to store lists efficiently.

List Application Scenarios

User, product, or comment lists.

Message queues.

Stack implementations.

Redis Set Commands

Sets store unique, unordered elements.

sadd      key member1 member2 …   # Add members to a set
smembers   key                     # Retrieve all members
sismember  key member               # Check if a member exists
scard      key                     # Get the number of members
srem       key member               # Remove a member
srandmember key                    # Return a random member (without removal)
spop       key                     # Remove and return a random member
smove      source dest member       # Move a member from one set to another

Typical uses include deduplication, computing intersections/unions/differences, and tracking unique visitors.

Set Application Scenarios

Website unique visitor (UV) counting.

Finding mutual friends.

Redis Sorted Set Commands

Sorted sets associate a score with each member, keeping them ordered by score.

zadd      key score1 member1 score2 member2 …   # Add members with scores
zrem      key member1 member2 …                # Remove members
zcard     key                                 # Number of members
zcount    key min max                         # Count members with scores in range
zincrby   key increment member                # Increment a member's score
zscore    key member                          # Get a member's score
zrank     key member                          # Rank (ascending)
zrevrank key member                          # Rank (descending)
zrange    key start stop [WITHSCORES]         # Get members in score order (asc)
zrevrange key start stop [WITHSCORES]         # Get members in score order (desc)

Sorted sets are ideal for ranking systems such as sales leaderboards or click‑through rankings.

Redis Hash Commands

Hashes map fields to values within a single key, perfect for representing objects.

hset      key field value          # Set a field
hget      key field                # Get a field
hmset     key field1 val1 field2 val2 … # Set multiple fields
hmget     key field1 field2 …      # Get multiple fields
hgetall   key                     # Retrieve all fields and values
hdel      key field1 field2 …      # Delete fields
hlen      key                     # Number of fields
hkeys     key                     # List all field names
hincrby   key field increment      # Increment integer field
hincrbyfloat key field increment # Increment floating‑point field
hsetnx    key field value          # Set if field does not exist

Typical scenario: shopping cart storage where the key is cart:{user_id}, each field is a product ID, and the value is the quantity.

HSET cart:123 1001 1          # Add product 1001 with quantity 1
HINCRBY cart:123 1001 1       # Increment quantity
HLEN cart:123                 # Number of distinct products
HDEL cart:123 1001            # Remove a product
HGETALL cart:123              # Retrieve the whole cart

After fetching the cart, the application can query the product database for detailed information.

For further learning, refer to official Redis documentation and advanced tutorials.