 CREATE TABLE books (
    book_id INT PRIMARY KEY,
    title VARCHAR(255),
    author VARCHAR(255),
    price DECIMAL(10, 2),
    amount INT
);

INSERT INTO books (book_id, title, author, price, amount) VALUES
(1, 'Мастер и Маргарита', 'Булгаков М.А.', 670.99, 3),
(2, 'Белая гвардия', 'Булгаков M.A.', 540.50, 5),
(3, 'Идиот', 'Достоевский Ф.М.', 460.00, 10),
(4, 'Братья Карамазовы', 'Достоевский Ф.М.', 799.01, 3),
(5, 'Игрок', 'Достоевский ф.М.', 480.50, 10),
(6, 'Стихотворения и поэмы', 'Есенин C.A.', 650.00, 15);

-- 1. Выведите информацию о книгах, цены которых меньше или равны средней цене книг на складе.
-- Информацию вывести в отсортированном по убыванию цены виде.
SELECT author, title, amount, price
FROM books
WHERE price <= (SELECT AVG(price) FROM books)
ORDER BY price DESC;

-- 2. Выведите информацию о книгах тех авторов, общее количество экземпляров книг которых не менее 10.
SELECT author, SUM(amount) AS total_amount
FROM books
GROUP BY author
HAVING SUM(amount) >= 10;

-- 3. Выведите информацию о книгах, цены которых превышают минимальную цену книги на складе не более чем на 150 рублей.
-- Отсортировать по возрастанию цены.
SELECT author, title, price
FROM books
WHERE price > (SELECT MIN(price) FROM books) AND price <= (SELECT MIN(price) + 150 FROM books)
ORDER BY price;

-- 4. Выведите информацию о книгах, количество экземпляров которых в таблице не дублируется.
SELECT author, title, amount
FROM books
GROUP BY author, title, amount
HAVING COUNT(*) = 1;

-- 5. Выведите информацию о книгах, количество которых меньше самого большого среднего количества книг каждого автора.
SELECT author, title, amount
FROM books
WHERE amount < (SELECT MAX(avg_amount) FROM (SELECT author, AVG(amount) as avg_amount FROM books GROUP BY author) as subquery);

-- 6. Выведите информацию о книгах, цена которых меньше самой большой из минимальных цен для каждого автора.
SELECT author, title, price
FROM books
WHERE price < (SELECT MAX(min_price) FROM (SELECT author, MIN(price) as min_price FROM books GROUP BY author) as subquery);

-- 7. Выведите информацию о книгах, количество экземпляров которых отличается от среднего количества экземпляров на складе более чем на 5.
-- Указать среднее значение количества экземпляров книг.
SELECT author, title, amount
FROM books
WHERE ABS(amount - (SELECT AVG(amount) FROM books)) > 5;

-- 8. Посчитайте сколько и каких экземпляров книг нужно заказать поставщикам,
-- чтобы на складе стало одинаковое количество экземпляров каждой книги,
-- равное значению самого большего количества экземпляров одной книги на складе.
WITH MaxAmount AS (
    SELECT MAX(amount) as max_amount
    FROM books
)
SELECT title, author, amount, (SELECT max_amount - amount FROM MaxAmount) as "Заказ"
FROM books;

-- 9. Узнайте на сколько отличаются по стоимости книги от книги с максимальной стоимостью.
SELECT title, ABS(price - (SELECT MAX(price) FROM books)) as "отмаксимальнойстоимости"
FROM books;

created 1 year ago

MySQL online editor

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

About MySQL

MySQL is a open-source, free and very popular relational database management system which is developed, distributed and supported by Oracle corporation.

Key Features:

Open-source relational database management systems.
Reliable, very fast and easy to use database server.
Works on client-server model.
Highly Secure and Scalable
High Performance
High productivity as it uses stored procedures, triggers, views to write a highly productive code.
Supports large databases efficiently.
Supports many operating systems like Linux*,CentOS*, Solaris*,Ubuntu*,Windows*, MacOS*,FreeBSD* and others.

Syntax help

Commands

1. CREATE

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

Example

CREATE TABLE EMPLOYEE (
  empId INTEGER PRIMARY KEY,
  name TEXT NOT NULL,
  dept TEXT NOT NULL
);

2. ALTER

ALTER TABLE Table_name ADD column_name datatype;

Example

INSERT INTO EMPLOYEE VALUES (0001, 'Dave', 'Sales');

3. TRUNCATE

TRUNCATE table table_name;

4. DROP

DROP TABLE table_name;

5. RENAME

RENAME TABLE table_name1 to new_table_name1;

6. COMMENT

Single-Line Comments:

 --Line1;

Multi-Line comments:

   /* Line1,
   Line2 */

DML Commands

1. INSERT

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

Note: Column names are optional.

Example

INSERT INTO EMPLOYEE VALUES (0001, 'Ava', 'Sales');

2. SELECT

SELECT column1, column2, ...
FROM table_name
[where condition];

Example

SELECT * FROM EMPLOYEE where dept ='sales';

3. UPDATE

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

Example

UPDATE EMPLOYEE SET dept = 'Sales' WHERE empId='0001';

4. DELETE

DELETE FROM table_name where condition;

Example

DELETE from EMPLOYEE where empId='0001';

Indexes

1. CREATE INDEX

  CREATE INDEX index_name on table_name(column_name);

To Create Unique index:

  CREATE UNIQUE INDEX index_name on table_name(column_name);

2. DROP INDEX

DROP INDEX index_name ON table_name;

Views

1. Create a View

Creating a View:
CREATE VIEW View_name AS 
Query;

2. How to call view

SELECT * FROM View_name;

3. Altering a View

ALTER View View_name AS 
Query;

4. Deleting a View

DROP VIEW View_name;

Triggers

1. Create a Trigger

CREATE TRIGGER trigger_name trigger_time trigger_event
    ON tbl_name FOR EACH ROW [trigger_order] trigger_body
/* where
trigger_time: { BEFORE | AFTER }
trigger_event: { INSERT | UPDATE | DELETE }
trigger_order: { FOLLOWS | PRECEDES } */

2. Drop a Trigger

DROP TRIGGER [IF EXISTS] trigger_name;

Stored Procedures

1. Create a Stored Procedure

CREATE PROCEDURE sp_name(p1 datatype)
BEGIN
/*Stored procedure code*/
END;

2. How to call Stored procedure

CALL sp_name;

3. How to delete stored procedure

DROP PROCEDURE sp_name;

Joins

1. INNER JOIN

SELECT * FROM TABLE1 INNER JOIN TABLE2 where condition;

2. LEFT JOIN

SELECT * FROM TABLE1 LEFT JOIN TABLE2 ON condition;

3. RIGHT JOIN

SELECT * FROM TABLE1 RIGHT JOIN TABLE2 ON condition;

4. CROSS JOIN

SELECT select_list from TABLE1 CROSS JOIN TABLE2;