Redis is a type of database and more specificaly is a NoSQL database. It's not like the other NoSQL databases or like a SQL database (such as MongoDB, PostgreSQL or MySQL) because Redis doesn't have the concept of "document" nor of "table".
All of the data in Redis is stored in key, value pairs. Think about Redis as one big giant JSON file.
Unlike the other databases than run on disk, Redis runs on RAM (on memory) and this makes it very fast but also volatile.
This is why Redis is generally used for caching: it has to be accessed often and it has to be quick.
If you're on Mac, install Redis with brew as follows:
brew install redis
| Command | Description |
|---|---|
redis-server |
Starts the redis server on your machine |
redis-cli |
Starts the CLI |
quit |
If executed in the CLI, it quits the CLI |
SET name John |
Creates an entry "name": "John" |
GET name |
Returns the value of the key "name" |
DEL name |
Deletes the entry with key "name" |
EXISTS name |
Checks if the entry with key "name" exists, returns 1 (true) or 0 (false) |
KEYS * |
Returns a list of all the keys |
FLUSHALL |
Deletes everything from the database |
TTL name |
Returns the time to live* (in seconds) of the entry with key "name". -1 means the entry has no expiration |
EXPIRE name 10 |
Sets the time to live of the entry with key "name" to 10 seconds |
SETEX name 10 John |
Creates an entry "name": "John" and sets its time to live to 10 seconds |
LPUSH friends John |
Creates an entry "friends" that has "John" inside of the array |
LRANGE friends 0 -1 |
Returns a list of items in the array "friends" |
LPUSH friends Sally |
Appends the item "Sally" on the "right" of the array "friends" |
LPOP friends |
Removes the first item of the array "friends" and returns it |
SADD hobbies "playing guitar" |
Creates a set* "hobbies" and adds the member "playing guitar" |
SMEMBERS hobbies |
Returns a list of items in the set "hobbies" |
SREM hobbies "playing guitar" |
Removes the item "playing guitar" from the set "hobbies" and returns 1 if successful, 0 otherwise |
HSET person name John |
Create a hash "person" with an entry "name": "John" |
HGET person name |
Returns the value of the entry with key "name" in the hash "person" |
HGETALL person |
Returns all the pairs key, value of the hash "person" |
HDEL person name |
Deletes the key, value pair with key "name" in the hash "person" |
HEXISTS person name |
Checks if the entry with key "name" exists in the hash "person", returns 1 (true) or 0 (false) |
*Time to live (TTL) is the time that an object is stored in a caching system before it's deleted or refreshed. *Sets cannot have duplicate members