如何在sql中以固定日期间隔获取记录

Question

The federal aviation authority wants to know how many types of aircraft each of your pilots (employee only ie EMP) is currently certified (qualifies) to fly. Assume that the validity of a certification is only for one year . So, list the pilots and the number of types of aircraft each is currently qualified to fly (date_certified). Please list pilot full name, license number, and number of types s/he is currently qualified (certified) to fly. (hint: SYSDATE returns today's date like date() in MS Access. (SYSDATE +30) is 30 days from today).

HERE IS THE PILOT TABLE:

pilot_nbr, license_nbr, last_name, first_name, title, address, phone, office_nbr, contract_type, salary, manager_nbr  

'701', '7111', 'Dark', 'Jack', '1st officer', '6 street', '6042233445', '789', 'PTE', '145000.00', NULL
'702', '7222', 'Mack', 'Bill', '1st officer', '7 street', '6043344556', '890', 'EMP', '155000.00', '701'
'703', '7333', 'Cheung', 'Charles', '2nd officer', '8 street', '6044455667', '503', 'PTE', '140000.00', '701'
'704', '7444', 'Gordon', 'Greg', '1st officer', '9 street', '6045566778', '123', 'EMP', '125000.00', '701'
'705', '7555', 'Basso', 'Nicki', '2nd officer', '5 street', '6046677889', '223', 'EMP', '163000.00', '701'
'706', '7666', 'Vettel', 'Sebast', '1st officer', '5 street', '6046677800', '523', 'EMP', '199000.00', '701'
'707', '7777', 'Hawke', 'Mike', '2nd officer', '7 street', '6046677326', '423', 'EMP', '139000.00', '701'  

HERE IS THE QUALIFIES TABLE:

pilot_nbr, plane_type, date_certified  

'701', 'DE Prop', '2013-08-14'
'701', 'SE Prop', '2013-04-10'
'702', 'DE Prop', '2013-02-22'
'702', 'SE Jet', '2013-04-10'
'702', 'SE Prop', '2013-06-21'
'703', 'DE Prop', '2013-04-10'
'703', 'SE Jet', '2013-04-10'
'703', 'SE Prop', '2013-04-10'
'704', 'DE Prop', '2013-06-12'
'704', 'ME Jet', '2013-08-21'
'704', 'SE Jet', '2013-06-15'
'704', 'SE Prop', '2013-04-10'  

HERE IS WHAT I TRIED (DON'T KNOW IF IT IS CORRECT)

SELECT first_name, last_name, license_nbr, Count(first_name) As 'No of types of airplane certified to fly'
FROM pilot, qualifies 
WHERE pilot.pilot_nbr=qualifies.pilot_nbr AND contract_type='EMP' AND date_certified >=  DATE_SUB(NOW(), INTERVAL 1 YEAR)
GROUP BY first_name, last_name  

Your help will be appreciated.

Answer 1

Hope this will solve your task...

SELECT p.first_name, p.last_name, p.license_nbr, Count(q.plane_type) As 'No of types of airplane certified to fly'
FROM pilot p inner join qualifies q on p.pilot_nbr = q.pilot_nbr
WHERE p.contract_type='EMP' AND DATE_SUB(q.date_certified, INTERVAL 1 YEAR) > CURDATE()
GROUP BY p.first_name, p.last_name, p.license_nbr;