mysql - 如何获得唯一 ID 和 MAX(日期)？

Question

有人可以帮助我吗？我不知道我认为是正确的查询有什么问题..

项目表

贷款表

典当 table

贷款分配表

这是我获取唯一 ID 和 MAX(date) 的查询

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^查询的结果是这样的:

我喜欢发生的结果是下面这个

Answer 1

根据评论，如果您想要每个 pawner_id 的最高 date_loan_granted 值，而不是每个 (pawner_id, item_id)，您可能需要:

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