-- create
CREATE TABLE buyers (
  buyer_id INTEGER PRIMARY KEY,
  name TEXT NOT NULL,
  city TEXT NOT NULL
);
CREATE TABLE products (
  product_id INTEGER PRIMARY KEY,
  product_name TEXT NOT NULL,
  price INTEGER NOT NULL
);
CREATE TABLE orders (
  order_id INTEGER NOT NULL,
  order_date DATE NOT NULL,
  buyer_id INTEGER references buyers (buyer_id),
  product_id INTEGER NOT NULL,
  quantity INTEGER NOT NULL,
  PRIMARY KEY (order_id, product_id)
);


-- insert
INSERT INTO buyers VALUES (1, 'Марина Сидорова', 'Москва');
INSERT INTO buyers VALUES (2, 'Иван Иванов', 'Москва');
INSERT INTO buyers VALUES (3, 'Андрей Сидоров', 'Тверь');
INSERT INTO buyers VALUES (4, 'Майнер', 'Иркутск');

INSERT INTO products VALUES (123, 'процессор', 20000);
INSERT INTO products VALUES (234, 'видеокарта', 80000);
INSERT INTO products VALUES (345, 'жёсткий диск', 6000);
INSERT INTO products VALUES (456, 'материнская плата', 10000);
INSERT INTO products VALUES (567, 'телефон', 30000);
INSERT INTO products VALUES (678, 'ноутбук', 60000);
INSERT INTO products VALUES (789, 'клавиатура', 3000);
INSERT INTO products VALUES (890, 'мышь', 2000);
INSERT INTO products VALUES (012, 'оперативная память', 8000);


INSERT INTO orders VALUES (100, '2023-06-01', 3, 123, 1);
INSERT INTO orders VALUES (102, '2023-06-01', 2, 234, 1);
INSERT INTO orders VALUES (101, '2023-02-20', 1, 678, 1);
INSERT INTO orders VALUES (102, '2024-10-12', 2, 345, 2);
INSERT INTO orders VALUES (100, '2023-06-01', 3, 456, 1);
INSERT INTO orders VALUES (103, '2025-01-16', 2, 567, 1);
INSERT INTO orders VALUES (104, '2024-07-31', 1, 789, 1);
INSERT INTO orders VALUES (104, '2024-07-31', 1, 890, 1);
INSERT INTO orders VALUES (100, '2023-06-01', 3, 012, 4);
INSERT INTO orders VALUES (105, '2023-06-01', 4, 234, 5);
INSERT INTO orders VALUES (101, '2023-02-20', 1, 567, 1);
INSERT INTO orders VALUES (106, '2023-02-20', 2, 567, 1);
INSERT INTO orders VALUES (106, '2023-02-20', 2, 012, 1);

-- fetch 
WITH total AS (
  SELECT buyers.buyer_id, buyers.name, SUM(orders.quantity * products.price) AS total_order
  FROM buyers
  INNER JOIN orders ON orders.buyer_id = buyers.buyer_id
  INNER JOIN products ON products.product_id = orders.product_id
  GROUP BY buyers.buyer_id, orders.order_id)
SELECT name FROM (
  SELECT name, SUM(total_order) AS sum_bought FROM total
  GROUP BY buyer_id, name) AS max_bought
ORDER BY sum_bought DESC LIMIT 1

PostgreSQL online editor

Write, Run & Share PostgreSQL queries online using OneCompiler's PostgreSQL online editor and compiler for free. It's one of the robust, feature-rich online editor and compiler for PostgreSQL. Getting started with the OneCompiler's PostgreSQL editor is really simple and pretty fast. The editor shows sample boilerplate code when you choose database as 'PostgreSQL' and start writing queries to learn and test online without worrying about tedious process of installation.

About PostgreSQL

PostgreSQL is a open source relational database system and is also knows as Postgres.

Key Features:

  • Postgres is not only free and open-source but also it is highly extensible.
  • Custom Data types and funtions from various programming languaues can be introduced and the good part is compiling entire database is not required.
  • ACID(Atomicity, Consistency, Isolation, Durability) compliant.
  • First DBMS which implemented Multi-version concurrency control (MVCC) feature.
  • It's the default database server for MacOS.
  • It supports all major operating systems like Linux, Windows, OpenBSD,FreeBSD etc.

Syntax help

1. CREATE

CREATE command is used to create a table, schema or an index.

Syntax:

         CREATE TABLE table_name (
                column1 datatype,
                column2 datatype,
                ....);

2. ALTER

ALTER command is used to add, modify or delete columns or constraints from the database table.

Syntax

ALTER TABLE Table_name ADD column_name datatype;

3. TRUNCATE:

TRUNCATE command is used to delete the data present in the table but this will not delete the table.

Syntax

TRUNCATE table table_name;

4. DROP

DROP command is used to delete the table along with its data.

Syntax

DROP TABLE table_name;

5. RENAME

RENAME command is used to rename the table name.

Syntax

ALTER TABLE table_name1 RENAME to new_table_name1;

6. INSERT

INSERT Statement is used to insert new records into the database table.

Syntax

INSERT INTO table_name (column1, column2, column3, ...) VALUES (value1, value2, value3, ...);

7. SELECT

Select statement is used to select data from database tables.

Syntax:

SELECT column1, column2, ...
FROM table_name;

8. UPDATE

UPDATE statement is used to modify the existing values of records present in the database table.

Syntax

UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;

9. DELETE

DELETE statement is used to delete the existing records present in the database table.

Syntax

DELETE FROM table_name where condition;