Database homework

1,
SELECT title, first_name, last_name, start_date, end_date, CONCAT(title, '. ', first_name, ' ', last_name, ' (', start_date, ' - ', IF(end_date is NULL, "no end date", end_date), ')') AS information
FROM employee;

2,
ALTER TABLE `account` DROP FOREIGN KEY `account_customer_fk`;
ALTER TABLE `account` ADD CONSTRAINT `account_customer_fk` FOREIGN KEY (`cust_id`) REFERENCES `customer`(`cust_id`) ON DELETE RESTRICT ON UPDATE CASCADE;

ALTER TABLE `business` DROP FOREIGN KEY `business_employee_fk`;
ALTER TABLE `business` ADD CONSTRAINT `business_employee_fk` FOREIGN KEY (`cust_id`) REFERENCES `customer`(`cust_id`) ON DELETE RESTRICT ON UPDATE CASCADE;

ALTER TABLE `individual` DROP FOREIGN KEY `individual_customer_fk`;
ALTER TABLE `individual` ADD CONSTRAINT `individual_customer_fk` FOREIGN KEY (`cust_id`) REFERENCES `customer`(`cust_id`) ON DELETE RESTRICT ON UPDATE CASCADE;

ALTER TABLE `officer` DROP FOREIGN KEY `officer_customer_fk`;
ALTER TABLE `officer` ADD CONSTRAINT `officer_customer_fk` FOREIGN KEY (`cust_id`) REFERENCES `customer`(`cust_id`) ON DELETE RESTRICT ON UPDATE CASCADE;

UPDATE customer
SET cust_id = CONCAT('100', cust_id);

UPDATE customer
SET cust_id = SUBSTR(cust_id, 4);

3,
INSERT INTO `customer` (`cust_id`, `address`, `city`, `cust_type_cd`, `fed_id`, `postal_code`, `state`)
VALUES (NULL, 'Tan Binh', 'Ho Chi Minh', 'h', 'ha', '01942', 'mm'),
	(NULL, 'somewhere', 'Ha Noi', 'a', 'xx', '12344', 'ma'),
    (NULL, 'asgard', 'My Tho', 'b', 'na', '34444', 'ma');

SELECT postal_code, COUNT(postal_code) AS num_customers
FROM `customer`
GROUP BY postal_code
HAVING postal_code is not NULL;

4,
SELECT txn_id, amount, CAST(txn_date AS DATE) AS date
FROM `acc_transaction`
WHERE 1;

5,
SELECT *, (YEAR(CURRENT_DATE()) - YEAR(birth_date)) AS age
FROM `individual`
HAVING age > 50
ORDER BY age;

6,
SELECT CONCAT(LEFT(first_name, 1), RIGHT(first_name, 1), '. ', last_name) AS name, title
FROM `employee`
WHERE title LIKE '%teller%'