Question

假设我有这样的oracle表。

EMP_ID    DATE_EX       ATTN   LEV   REV
--------  -----------   ----   ----  ----
50001000  13-07-2017    22     02    1
50001000  19-08-2017    26     04    2
50001001  30-06-2017    20     05    3
50001000  17-09-2017    20     05    4
50001000  19-08-2017    25     05    5
50001001  27-07-2017    21     04    6
50001000  17-09-2017    26     02    7
50001000  13-07-2017    21     04    8

我想获得最后更新的单行，其最大DATE_EX和最大REV。

我的预期输出是

输出：

EMP_ID    DATE_EX       ATTN   LEV   REV
--------  -----------   ----   ----  ----
50001000  17-09-2017    26     02    7

我正在寻找一个有效的SQL查询。请帮忙.. 查询必须兼容oracle 10g

Answer 1

规范方法是：

select t.*
from (select t.*
      from t
      order by t.date_ex desc, t.rev desc
     ) t
where rownum = 1;

如果您关心效果，则需要(date_ex desc, rev desc)上的索引。

Answer 2

最有效的查询 - 特别是它不需要子查询 - 使用FIRST / LAST聚合函数，如下所示。当最大DATE_EX没有“关联”时（DATE_EX的关系最大REV），这种方法效果最佳。

with
   test_data ( emp_id, date_ex, attn, lev, rev ) as (
     select 50001000, to_date('13-07-2017', 'dd-mm-yyyy'), 22, '02', 1 from dual union all
     select 50001000, to_date('19-08-2017', 'dd-mm-yyyy'), 26, '04', 2 from dual union all
     select 50001001, to_date('30-06-2017', 'dd-mm-yyyy'), 20, '05', 3 from dual union all
     select 50001000, to_date('17-09-2017', 'dd-mm-yyyy'), 20, '05', 4 from dual union all
     select 50001000, to_date('19-08-2017', 'dd-mm-yyyy'), 25, '05', 5 from dual union all
     select 50001001, to_date('27-07-2017', 'dd-mm-yyyy'), 21, '04', 6 from dual union all
     select 50001000, to_date('17-09-2017', 'dd-mm-yyyy'), 26, '02', 7 from dual union all
     select 50001000, to_date('13-07-2017', 'dd-mm-yyyy'), 21, '04', 8 from dual
   )
--  End of simulated inputs (for testing purposes only, not part of the solution).
--  SQL query begins BELOW THIS LINE.
select max(emp_id)  keep (dense_rank last order by date_ex, rev) as emp_id,
       max(date_ex)                                              as date_ex,
       max(attn)    keep (dense_rank last order by date_ex, rev) as attn,
       max(lev)     keep (dense_rank last order by date_ex, rev) as lev,
       max(rev)     keep (dense_rank last order by date_ex)      as rev
from   test_data
;

EMP_ID    DATE_EX     ATTN  LEV  REV
--------  ----------  ----  ---  ---
50001000  17-09-2017    26  02     7

Answer 3

如果您使用的是Oracle 12.1或更高版本，那么它只是：

select * from yourtable
order by date_ex desc, rev desc
fetch first row only;

Oracle：选择最后更新的行，其最大DATE_COLUMN

输出：

3 个答案: