💻 Примеры

⚡ Кратко: примеры

Типы данных: INT, DECIMAL, VARCHAR, BOOLEAN, DATE.
Преобразование: CAST('123' AS SIGNED), CAST(id AS CHAR).
Даты: NOW(), DATE_ADD, DATEDIFF, DATE_FORMAT.
Скрытые преобразования: '100' + 50, CONCAT('Total: ', 150).

💻 Примеры

Типы данных на практике

CREATE TABLE products_example (
    id INT PRIMARY KEY,
    name VARCHAR(255),
    price DECIMAL(10, 2),
    in_stock BOOLEAN,
    created_at DATETIME
);

Явное преобразование через CAST

SELECT CAST('123' AS SIGNED) AS number;
SELECT CAST(id AS CHAR(10)) AS id_string FROM customers;
SELECT CAST('2024-08-25' AS DATE) AS converted_date;

Скрытые преобразования в MySQL

SELECT '100' + 50 AS arithmetic_result;
SELECT CONCAT('The total amount is ', 150) AS message;
SELECT * FROM products WHERE unit_in_stock = '50';

Работа с датами

SELECT NOW() AS current_datetime;
SELECT CURDATE() AS current_date;

SELECT id, order_date, DAYNAME(order_date) AS day_of_week
FROM orders;

SELECT id, order_date,
       DATE_ADD(order_date, INTERVAL 30 DAY) AS new_order_date
FROM orders;

SELECT id, order_date, shipped_date,
       DATEDIFF(shipped_date, order_date) AS days_to_ship
FROM orders;

SELECT id, order_date
FROM orders
WHERE DAYOFWEEK(order_date) = 6;

Форматирование даты

SELECT DATE_FORMAT(NOW(), '%d-%m-%Y %H:%i:%s') AS formatted;