MySQL 8.0

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SET FOREIGN_KEY_CHECKS=0;
-- -----------------------------------------------------
-- Table `Music_store`.`customers`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `customers` (
  `customer_id` INT NOT NULL AUTO_INCREMENT,
  `customer_firstname` VARCHAR(45) NOT NULL,
  `customer_lastname` VARCHAR(45) NOT NULL,
  `customer_mobno` VARCHAR(20) NOT NULL,
  `music_store_store_id` INT NOT NULL,
  PRIMARY KEY (`customer_id`),
  INDEX `fk_customers_music_store1_idx` (`music_store_store_id` ASC) VISIBLE,
  UNIQUE INDEX `customer_mobno_UNIQUE` (`customer_mobno` ASC) VISIBLE,
  CONSTRAINT `fk_customers_music_store1`
    FOREIGN KEY (`music_store_store_id`)
    REFERENCES `music_store` (`store_id`)
    ON DELETE CASCADE
    ON UPDATE CASCADE)
ENGINE = InnoDB;
-- -----------------------------------------------------
-- Table `Music_store`.`orders`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `orders` (
  `order_id` INT NOT NULL AUTO_INCREMENT,
  `order_date` DATETIME NOT NULL,
  `ship_amount` INT NOT NULL,
  `tax_amount` INT NOT NULL,
  `ship_date` DATETIME NOT NULL,
  `customers_customer_id` INT NOT NULL,
  PRIMARY KEY (`order_id`),
  INDEX `fk_orders_customers1_idx` (`customers_customer_id` ASC) VISIBLE,
  CONSTRAINT `fk_orders_customers1`
    FOREIGN KEY (`customers_customer_id`)
    REFERENCES `customers` (`customer_id`)
    ON DELETE CASCADE
    ON UPDATE CASCADE)
ENGINE = InnoDB;
INSERT INTO customers (customer_firstname, customer_lastname, customer_mobno, music_store_store_id)
        VALUES ("Prasanth", "Pandiselvan", "456-986-1234", 1);
INSERT INTO customers (customer_firstname, customer_lastname, customer_mobno, music_store_store_id)
        VALUES ("Dan", "Druar", "347-234-9876", 1);
INSERT INTO customers (customer_firstname, customer_lastname, customer_mobno, music_store_store_id)
        VALUES ("Lukeman", "Hakkim", "488-234-0987", 2);
INSERT INTO customers (customer_firstname, customer_lastname, customer_mobno, music_store_store_id)
        VALUES ("Paul", "Antony", "356-257-1233", 2);
INSERT INTO customers (customer_firstname, customer_lastname, customer_mobno, music_store_store_id)
        VALUES ("Nikhil", "Reddy", "678-234-1345", 3);
INSERT INTO customers (customer_firstname, customer_lastname, customer_mobno, music_store_store_id)
        VALUES ("Saravana", "Kumar", "456-986-2671", 3);
INSERT INTO customers (customer_firstname, customer_lastname, customer_mobno, music_store_store_id)
        VALUES ("Mugil", "Pandian", "877-285-3322", 4);
INSERT INTO orders (order_date, ship_amount, tax_amount, ship_date, customers_customer_id)
        Values("2020-03-03 22:59:52", "127", 4,  "2020-03-04 22:59:52", 1);
INSERT INTO orders (order_date, ship_amount, tax_amount, ship_date, customers_customer_id)
        Values("2020-03-13 22:59:52", "158", 5,  "2020-03-15 22:59:52", 1);
INSERT INTO orders (order_date, ship_amount, tax_amount, ship_date, customers_customer_id)
        Values("2020-02-08 22:59:52", "201", 5,  "2020-02-10 22:59:52", 2);
INSERT INTO orders (order_date, ship_amount, tax_amount, ship_date, customers_customer_id)
        Values("2020-02-25 22:59:52", "300", 6,  "2020-02-27 22:59:52", 2);
INSERT INTO orders (order_date, ship_amount, tax_amount, ship_date, customers_customer_id)
        Values("2020-05-14 22:59:52", "500", 7,  "2020-05-16 22:59:52", 3);
INSERT INTO orders (order_date, ship_amount, tax_amount, ship_date, customers_customer_id)
        Values("2020-02-08 22:59:52", "557", 7,  "2020-02-12 22:59:52", 3);
INSERT INTO orders (order_date, ship_amount, tax_amount, ship_date, customers_customer_id)
        Values ("2020-06-19 22:59:52", "658", 7,  "2020-06-21 22:59:52", 4);
SET FOREIGN_KEY_CHECKS=1;
SELECT customers_customer_id, COUNT(*) count_r 
FROM orders
GROUP BY customers_customer_id
HAVING count_r = ( 
SELECT MAX(count_r) FROM (SELECT COUNT(*) count_r FROM `orders` GROUP BY customers_customer_id) t1)


customers_customer_id
count_r


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