Master Redis: Explore Strings, Lists, Sets, Hashes, and Sorted Sets

Preface

Redis can store keys and five common data types: String, List, Set, Hash, and ZSet. Some commands are shared across types, while others are specific to each structure.

Below is a comparison of the five Redis data structures.

Now we introduce the five different data structure types.

String type

In Redis, a String is a sequence of bytes, similar to string operations in other programming languages.

An example with key hello and value world:

(1) Common commands:

(2) Increment and decrement commands:

(3) Additional operations:

1. Get string length 2. Append content 3. Get/set substring 4. Get/set bit 5. Set multiple strings

Illustrated below:

(4) Use cases:

String is the most common type; ordinary key/value storage belongs here. Values can also be numbers, e.g., counting how many times an IP address exceeds a threshold. The INCRBY command makes atomic increments easy.

List type

Redis List is implemented as a doubly linked list. It is useful for timelines, message queues, and other ordered collections.

An example list where elements can repeat:

Note: A List stores ordered strings and allows duplicate elements.

(1) Common commands:

LPUSH

and RPUSH push elements to the left or right; LPOP and RPOP pop elements from the left or right.

Using LRANGE with start 0 and end -1 returns all elements.

(2) Additional commands allow removing elements, inserting in the middle, trimming to a specific length, etc.

(3) Use cases:

Weibo timeline

Message queue

Set type

A Set stores unique unordered strings; duplicate entries are automatically eliminated.

Unlike List, a Set cannot push or pop elements from ends.

Example Set with distinct elements:

(1) Common commands:

(2) Set operations include intersection, union, and difference:

(3) Use cases:

Finding mutual or second-degree friends

Counting distinct IP addresses

Friend recommendation by intersecting tag sets

Hash type

A Hash stores a mapping of multiple field‑value pairs. Values can be strings or numbers, and numeric fields can be incremented or decremented.

Example hash with two fields:

(1) Common commands:

(2) Additional commands for adding/deleting fields, retrieving all fields, and incrementing/decrementing numeric values:

Sorted Set (ZSet) type

A Sorted Set stores unique members with a floating‑point score. It allows access by member and by score order, enabling range queries based on scores.

Example ZSet with two elements:

(1) Common commands:

Reference articles:

http://blog.csdn.net/gaogaoshan/article/details/41039581/

Redis in Action – Josiah L. Carlson