如何在sql中检索上月最新日期和本月最新日期

预期产出： 我需要查看一行中的数据，获取最新的seq no details和lastusagedate作为之前的seq no 9 LastDate

create table imsi_data(account varchar2(20)not null,imsi number(10),seqno number(20) not null,package_id number(10),event_date date)

insert into imsi_data values('10001',123456,09,164,add_months((sysdate),-2));
insert into imsi_data values('10001',123456,09,164,add_months((sysdate-1),-2));
insert into imsi_data values('10001',123456,09,164,add_months((sysdate-2),-2));
insert into imsi_data values('10001',123456,10,165,add_months((sysdate),-1));
insert into imsi_data values('10001',123456,10,165,add_months((sysdate-1),-1));
insert into imsi_data values('10001',123456,10,165,add_months((sysdate-2),-1));

select * from imsi_data

ACCOUNT IMSI    SEQNO   PACKAGE_ID  EVENT_DATE       

1   10001   123456    9      164       9/4/2015 4:17:06 AM  
2   10001   123456    9      164       9/3/2015 4:17:18 AM  
3   10001   123456    9      164       9/2/2015 4:18:16 AM  
4   10001   123456   10      165      10/4/2015 4:18:34 AM  
5   10001   123456   10      165      10/3/2015 4:23:23 AM  
6   10001   123456   10      165      10/2/2015 4:23:31 AM  

我的sql在这里：

ACCOUNT IMSI  SEQNO   PACKAGEID  LastUsageDate        CurrentUsageDate 

10001   123456 10       165     9/4/2015 4:17:06 AM    10/4/2015 4:18:34 AM

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这将lastusagedate设置为null。但是我应该得到之前的seq max事件日期。有人能帮我吗：

你可以尝试以下方法：

select account,
       imsi,
       lastusage_date,
       current_date,
       package_id,
       seqno
from (
   select ce.package_id,
          ce.seqno,
          ce.account,
          ce.IMSI,
          lag(ce.event_date) over(partition by ce.IMSI, ce.seqno order by ce.IMSI, ce.event_date desc) lastusage_date,
          ce.event_date current_date,
          row_number() over(partition by ce.imsi, ce.seqno order by ce.event_date desc) rn
   from imsi_data ce
    where ce.account = '10001' and ce.seqno in (10, 09)
    group by ce.account, ce.seqno, ce.imsi, ce.event_date, ce.package_id)
where rn =1

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请标记使用的数据库管理系统。当涉及到日期/时间时，它们中的太多都远远不符合ANSI SQL…”根据sysdate和varchar2的用法添加了oracle标记

select
    ce.account,
    ce.IMSI,
    ce.seqno,
    ce.package_id,
    (
      select 
          max(prev_seq_date_ivw.event_date) ev_date 
        from 
          imsi_data prev_seq_date_ivw 
        where 
          prev_seq_date_ivw.seqno = (
            select 
                max(prev_seq_ivw.seqno) 
              from 
                imsi_data prev_seq_ivw 
              where 
                prev_seq_ivw.seqno < ce.seqno
          )
    ) last_usage_date,
    max(ce.event_date) current_usage_date
  from imsi_data ce
  where ce.account = '10001' and ce.seqno in (10, 09)
  group by     
    ce.account,
    ce.IMSI,
    ce.seqno,
    ce.package_id;