SELECT YEAR(birthdate) birthyear FROM member GROUP BY YEAR(birthdate)

SELECT tag_name, birthdate, SUM(total_price) total_price
FROM
(SELECT product_code, SUM(amount*price) total_price FROM order_product GROUP BY product_code) T1
JOIN
(SELECT * FROM tag_product WHERE tag_name IN (SELECT member_code FROM member)) T2
USING(product_code)
GROUP BY tag_name

//SUM(price*amount) total_price, SUM(amount) amount

SELECT member_code, COUNT(unit_id) n FROM unit_member GROUP BY member_code

SELECT unit_id, FROM_UNIXTIME(AVG(UNIX_TIMESTAMP(birthdate))) avg_birth FROM (SELECT * FROM unit_member) T1
LEFT JOIN member USING(member_code)
GROUP BY unit_id

SELECT * FROM unit_member

SELECT `datetime` FROM event