Базы данных

SELECT * FROM users u
INNER JOIN orders o ON u.id = o.user_id;

SELECT * FROM users u
LEFT JOIN orders o ON u.id = o.user_id;

SELECT * FROM users u
RIGHT JOIN orders o ON u.id = o.user_id;

SELECT * FROM users u
FULL OUTER JOIN orders o ON u.id = o.user_id;

psql -U username -d database

\l

\dt

\d table_name

CREATE DATABASE dbname;

CREATE TABLE users (
  id SERIAL PRIMARY KEY,
  name VARCHAR(100)
);

mysql -u username -p database

SHOW DATABASES;

SHOW TABLES;

DESCRIBE table_name;

CREATE DATABASE dbname;

redis-cli

SET key "value"
GET key

EXPIRE key 3600  # секунды

KEYS pattern

DEL key

HSET user:1 name "John"
HGET user:1 name

LPUSH list "item"
LRANGE list 0 -1

mongosh

show dbs

use dbname

show collections

db.users.insertOne({name: "John", age: 30})

db.users.find({age: {$gt: 25}})

db.users.updateOne({name: "John"}, {$set: {age: 31}})

kafka-topics --create --topic my-topic --bootstrap-server localhost:9092

kafka-topics --list --bootstrap-server localhost:9092

kafka-console-producer --topic my-topic --bootstrap-server localhost:9092

kafka-console-consumer --topic my-topic --bootstrap-server localhost:9092 --from-beginning