如何在SQL中通过单独的行将多个时间段连接在一起？

我有一个包含唯一ID的SQL表和两个表示时间段（天）开始和结束的列。对于每个唯一的_id，如果行可以组合成一个连续的周期，我希望将它们连接在一起。例如，我有：

unique_id   start           end
A           2013-01-01      2013-01-02
A           2013-01-03      2013-01-05
A           2013-01-05      2013-01-07
A           2013-01-07      2013-01-09
A           2013-01-09      2013-01-11
B           2013-01-02      2013-01-03
B           2013-01-05      2013-01-06

我想：

unique_id   start           end
A           2013-01-01      2013-01-02
A           2013-01-03      2013-01-11
B           2013-01-02      2013-01-03
B           2013-01-05      2013-01-06

我们可以假设没有重叠的时期

我该怎么做

with TableX as(
 select * from (values ('A','2013-01-01'::date,'2013-01-02'::date),
('A','2013-01-03'::date,'2013-01-05'::date),
('A','2013-01-05'::date,'2013-01-07'::date),
('A','2013-01-07'::date,'2013-01-09'::date),
('A','2013-01-09'::date,'2013-01-11'::date),
('B','2013-01-02'::date,'2013-01-03'::date),
('B','2013-01-05'::date,'2013-01-06'::date),
('C','2013-01-03'::date,'2013-01-05'::date),
('C','2013-01-05'::date,'2013-01-07'::date),
('C','2013-01-07'::date,'2013-01-09'::date),
('C','2013-01-10'::date,'2013-01-12'::date),
('C','2013-01-12'::date,'2013-01-15'::date)
               ) X(unique_id, start, endd)
)


select distinct unique_id,
       min(start) over(partition by unique_id,grp) as start,
       max(endd)   over(partition by unique_id,grp) as endd
  from
  (
   select *, sum(new) over(partition by unique_id order by start) grp
     from
     (
      select A.*,
             case when start=lag(endd) over(partition by unique_id order by start)
                  then 0 else 1 end as new
        from TableX A
     ) B
  ) C
 order by unique_id, start

结果:

unique_id|start     |endd
A        |2013-01-01|2013-01-02
A        |2013-01-03|2013-01-11
B        |2013-01-02|2013-01-03
B        |2013-01-05|2013-01-06
C        |2013-01-03|2013-01-09
C        |2013-01-10|2013-01-15

结果:

unique_id|start     |endd
A        |2013-01-01|2013-01-02
A        |2013-01-03|2013-01-11
B        |2013-01-02|2013-01-03
B        |2013-01-05|2013-01-06
C        |2013-01-03|2013-01-09
C        |2013-01-10|2013-01-15

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您使用什么RDBMS？红移。基本上是PostgreSQL。你用什么关系数据库？红移。基本上是PostgreSQL。