Data Types and Common Commands in Redis

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String Operations

Common commands for string operations in Redis:

  • SET key value: Sets the value of a specified key.
    • Example: 127.0.0.1:6379> set age 20
    • The value set using the SET command is always stored as a string.
    • If the key already exists, the value will be updated; if the key does not exist, a new key-value pair will be created.
  • GET key: Retrieves the value of a specified key.
    • Example: 127.0.0.1:6379> get age
  • SETEX key seconds value: Sets the value of a specified key and its expiration time in seconds (commonly used for storing verification codes).
  • SETNX key value: Sets the value of a key only if the key does not already exist (commonly used for distributed locks).

Hash Operations

Redis hashes are mapping tables of string-type fields and values, particularly suitable for storing objects.

key field1 value1
field2 value2

Common commands:

  • HSET key field value: Sets the value of a field in the hash stored at a key.
  • HGET key field: Retrieves the value of a specified field in a hash.
  • HDEL key field: Deletes a specified field from a hash.
  • HKEYS key: Retrieves all fields in a hash (returns all fields of the specified key).
  • HVALS key: Retrieves all values in a hash.
  • HGETALL key: Retrieves all fields and values in a hash.

List Operations

Redis lists are simple string lists sorted by insertion order (ordered and can contain duplicates).

Key a b c d

Common commands:

  • LPUSH key value1 [value2]: Pushes one or more values onto the head of a list.
  • LRANGE key start stop: Retrieves elements within a specified range of a list. Use -1 for the last element (e.g., LRANGE key 0 -1).
  • RPOP key: Removes and retrieves the last element in a list.
  • LLEN key: Returns the length of a list.
  • BRPOP key1 [key2] timeout: Removes and retrieves the last element of a list. If the list is empty, the command blocks until a timeout or an element is available (commonly used for task queues).

Set Operations

Redis sets are unordered collections of string-type elements, where each element is unique (unordered and non-repeating).

Common commands:

  • SADD key member1 [member2]: Adds one or more members to a set.
  • SMEMBERS key: Retrieves all members of a set.
  • SCARD key: Returns the number of members in a set.
  • SINTER key1 [key2]: Returns the intersection of two or more sets.
  • SUNION key1 [key2]: Returns the union of two or more sets.
  • SDIFF key1 [key2]: Returns the difference between sets (elements unique to the first set).
  • SREM key member1 [member2]: Removes one or more members from a set.

Sorted Set Operations

Redis sorted sets are collections of unique string elements, each associated with a double-precision score for sorting.

Common commands:

  • ZADD key score1 member1 [score2 member2]: Adds one or more members to a sorted set or updates the score of existing members.
  • ZRANGE key start stop [WITHSCORES]: Retrieves members within a specified index range. Use [WITHSCORES] to include scores.
  • ZINCRBY key increment member: Increments the score of a specified member by a given value.
  • ZREM key member [member ...]: Removes one or more members from a sorted set.

General Key Commands

  • KEYS pattern: Finds all keys matching a given pattern (e.g., keys *).
  • EXISTS key: Checks if a key exists.
  • TYPE key: Returns the data type of the value stored at a key.
  • TTL key: Retrieves the time-to-live (TTL) of a key in seconds. A -1 indicates the key is set to persist indefinitely.
  • DEL key: Deletes a key if it exists.