我如何獲得唯一ID和MAX（日期）？

Question

請問有人能幫助我。我不知道是什麼毛病查詢我認爲這是是正確的..

項目表

貸款表

當戶表

Loan_assignment表

這是我得到的唯一的ID和MAX（日期）

SELECT distinct p.pawner_id, c.item_name, c.description, l.net_proceeds, 
max(DATE_FORMAT(a.date_loan_granted, '%d-%b-%Y')) as date 
from pawner p, loan l, collateral c, loan_assignment a, pawnshop b 
WHERE b.pawnshop_id = a.pawnshop_id AND p.pawner_id = a.pawner_id 
AND l.loan_id = a.loan_id AND a.item_id = c.item_id 
AND b.pawnshop_id = 1 group by p.pawner_id; 

上述^查詢結果查詢是這樣的：

，我想發生的結果是這樣的下面

Answer 1

試試這個：

SELECT distinct p.pawner_id, c.item_name, c.description, l.net_proceeds, 
DATE_FORMAT(MAX(a.date_loan_granted), '%d-%b-%Y') as date 
from pawner p, loan l, collateral c, loan_assignment a, pawnshop b 
WHERE b.pawnshop_id = a.pawnshop_id AND p.pawner_id = a.pawner_id 
AND l.loan_id = a.loan_id AND a.item_id = c.item_id 
AND b.pawnshop_id = 1 group by p.pawner_id; 

Answer 2

根據意見，如果你想爲每個pawner_id最高date_loan_granted價值，而不是每個（pawner_id，ITEM_ID）你可能反而想：

select m.pawner_id, 
     i.item_name, 
     i.description, 
     l.net_amount, 
     date_format(m.date_loan_granted, '%d-%b-%Y') as date_loan_granted 
    from (select pawner_id, 
       max(loan_id) as loan_id, 
       max(date_loan_granted) as date_loan_granted 
      from loan_assignment 
     group by pawner_id) m 
    join loan_assignment la 
    on m.pawner_id = la.pawner_id 
    and m.loan_id = la.loan_id 
    and m.date_loan_granted = l.date_loan_granted 
    join loan l 
    on m.loan_id = l.loan_id 
    join item i 
    on la.item_id = i.item_id