Sql ve两条记录。@user3014914:在这种情况下，您可能必须将计算更改为（按ass.person\u id，ass.effective\u start\u date划分）这对我帮助很大，它给了我一个想法，让我想出一个更好的解决方案，谢谢！@user30

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ve两条记录。@user3014914:在这种情况下，您可能必须将计算更改为

（按ass.person\u id，ass.effective\u start\u date划分）

这对我帮助很大，它给了我一个想法，让我想出一个更好的解决方案，谢谢！@user3014914:您能为这个问题添加您的解决方案吗？

select 
    ass.person_id, 
    ass.effective_start_date,
    ass.effective_end_date,
    exp.date_from, 
    exp.date_to, 
    exp.home_country, 
    exp.host_country
from expatriates exp, assignments ass
where 
    exp.person_id=ass.person_id
and exp.date_to >= ass.effective_start_date
and exp.date_to <= ass.effective_end_date

select 
distinct ass.person_id, 
ass.effective_start_date,
ass.effective_end_date,
exp.date_from, 
exp.date_to, 
exp.home_country, 
exp.host_country
from expatriates exp, assignments ass
where 
exp.person_id=ass.person_id
and exp.date_to >= ass.effective_start_date
and exp.date_from <= ass.effective_end_date

select 
ass.person_id, 
ass.effective_start_date,
ass.effective_end_date,
exp.date_from, 
exp.date_to, 
exp.home_country, 
exp.host_country
from expatriates exp, assignments ass
where 
exp.person_id=ass.person_id
and exp.date_to >= ass.effective_start_date
and exp.date_from <= ass.effective_end_date
and exp.status = 1

select 
    ass.person_id, 
    ass.effective_start_date,
    ass.effective_end_date,
    exp.date_from, 
    exp.date_to, 
    exp.home_country, 
    exp.host_country
from expatriates exp, assignments ass, (
    SELECT e.person_id, MAX(e.date_from) md
    FROM expatriates e
    INNER JOIN assignments a ON e.person_id=a.person_id
    and e.date_to >= a.effective_start_date
    and e.date_to <= a.effective_end_date GROUP BY e.person_id) X
where exp.person_id= X.person_id
and exp.date_from= X.md

active_or_last_ass AS (
    SELECT exp.person_id, date_from, max(exp.date_to) max_date
    FROM expatriates exp
    WHERE exp.date_from < sysdate
    GROUP BY exp.person_id, date_from
)   
select 
    ass.person_id, 
    ass.effective_start_date,
    ass.effective_end_date,
    exp.date_from, 
    exp.date_to, 
    exp.home_country, 
    exp.host_country
from 
    active_or_last_ass ala
    inner join expatriates exp 
       on  exp.person_id = ala.person_id
       and exp.date_to = ala.max_date
    inner join assignments ass
       on exp.person_id = ass.person_id

select *
from
 (
   select 
       ass.person_id, 
       ass.effective_start_date,
       ass.effective_end_date,
       exp.date_from, 
       exp.date_to, 
       exp.home_country, 
       exp.host_country,
       row_number() 
       over (partition by ass.person_id, ass.effective_start_date
             order by exp.date_from) as rn
   from expatriates exp, assignments ass
   where 
       exp.person_id=ass.person_id 
   and exp.date_to >= ass.effective_start_date
   and exp.date_to <= ass.effective_end_date
 ) dt
where rn = 1