Oracle：是否可以仅在重复出现时才过滤掉它们？答案

【问题标题】：Oracle: Is it possible to filter out duplicates only when they appear in succession?Oracle：是否可以仅在重复出现时才过滤掉它们？
【发布时间】：2020-12-01 11:39:26
【问题描述】：

提前感谢您的帮助。

我有一张表格，里面有司机的行程信息。有时行程似乎有相同的站点（但相隔几天）。我希望能够查询该表并过滤掉地址相同且日期连续的任何记录。

这可能吗？

再次感谢，乔什

【问题讨论】：

标签： oracle duplicates

【解决方案1】：

with tst as(
    select timestamp '2020-08-01 00:00:00' dt, '123 street' loc from dual
    union all
    select timestamp '2020-08-01 00:00:00', '89 street' from dual
    union all
    select timestamp '2020-08-02 00:00:00', '456 airport' from dual
    union all
    select timestamp '2020-08-04 00:00:00', '456 airport' from dual
    union all
    select timestamp '2020-08-05 00:00:00', '67 street' from dual
    union all
    select timestamp '2020-08-06 00:00:00', '89 street' from dual
    union all
    select timestamp '2020-08-07 00:00:00', '123 street' from dual
)
select dt, loc
from (
    select dt, loc, nvl(lag(loc) over(order by dt), 'FIRST_ROW') prev_loc
    from tst
) where loc <> prev_loc;

fiddle

【讨论】：

【解决方案2】：

另一种方法是使用Tabibitosan method，它为连续的行分配一个组号，然后计算每个组的行数。（在 asktom 网站上找到）。

with test_data as(
    select date'2020-08-01' dt, '123 street' loc from dual
    union all
    select date '2020-08-01', '89 street' from dual
    union all
    select date '2020-08-02', '456 airport' from dual
    union all
    select date '2020-08-04', '456 airport' from dual
    union all
    select date '2020-08-05', '67 street' from dual
    union all
    select date '2020-08-06', '89 street' from dual
    union all
    select date '2020-08-07', '123 street' from dual
)
select max(dt),loc
from
(
select t.*
  ,row_number() over (order by dt) -
   row_number() over (partition by loc order by dt) grp
  from test_data t
)
group by grp,loc
having count(*) > 1;

另一种使用 match_recognize 的方法从 12c 开始可用。使用 {1,} 的模式表示重复一次或多次

了解更多 match_recognize here

with test_data as(
    select date'2020-08-01' dt, '123 street' loc from dual
    union all
    select date '2020-08-01', '89 street' from dual
    union all
    select date '2020-08-02', '456 airport' from dual
    union all
    select date '2020-08-04', '456 airport' from dual
    union all
    select date '2020-08-05', '67 street' from dual
    union all
    select date '2020-08-06', '89 street' from dual
    union all
    select date '2020-08-07', '123 street' from dual
)
select * 
  from test_data
match_recognize (
  order by dt
  all rows per match
  pattern (equal{1,})
  define 
    equal as loc = prev(loc)
);

游乐场：Dbfiddle

【讨论】：