Redis data types

There are a total of five data types supported in redis,Respectively string string type，list type，Set type，Hash table type and ordered set zset type, Through these five different data types, we can achieve a variety of different functions, and can also be applied to a variety of different scenarios. Next, let’s take a look at the operation syntax of the five data types.

The structure of various data types in redis is as follows:

Operation of various data types in redis

Operations on String in Redis

The following table lists commonly used redis string commands

Operation of Hash list in Redis

• Redis hash is a mapping table of String type field and value. Hash is especially suitable for storing objects.
• Each hash in Redis can store 2³² -1 key-value pair (over 4 billion)

The following table lists the basic redis hash related commands:

Operation of List in Redis

• The Redis list is a simple list of strings, sorted in the order of insertion. You can add an element to the head (left) or tail (right) of the list
• A list can contain up to 2³² -1 element (4294967295, each list has more than 4 billion elements).

The following table lists the basic commands related to the list:

Operations on Set collections in Redis

• The Set of redis is an unordered collection of String type. Set members are unique, which means that no duplicate data can appear in the set.
• In Redis, collections are implemented through hash tables, so the complexity of adding, deleting, and looking up is O(1).
• The maximum number of members in the set is 2³² -1 (4294967295, each set can store more than 4 billion members).

The following table lists the basic commands of the Redis collection:

Key operations in Redis

The following table shows the basic commands related to Redis keys:

Database in Redis

Redis supports multiple databases, and the data of each database is isolated and cannot be shared, and is based on a single machine. If it is a cluster, there is no concept of a database.

Redis is a storage server with a dictionary structure. In fact, a Redis instance provides multiple dictionaries for storing data. The client can specify which dictionary to store the data in. This is similar to the well-known fact that multiple databases can be created in a relational database instance, so each dictionary can be understood as an independent database.

Each database is externally named with an increasing number starting from 0. Redis supports 16 databases by default (more can be supported through configuration files, no upper limit), and this number can be modified by configuring databases. After the client establishes a connection with Redis, it will automatically select the 0 database, but you can use the SELECT command to replace the database at any time. If you want to select the 1 database:

node01:6379> select 1
node01:6379[1]> keys *

Clear the data in the redis database

node01:6379> flushdb

Clear data in all redis databases

node01:6379> flushall