How to create a start and end date with no gaps from one date column and to sum a value within the dates

Question

I am new SQL coding using in SQL developer.

I have a table that has 4 columns: Patient ID (ptid), service date (dt), insurance payment amount (insr_amt), out of pocket payment amount (op_amt). (see table 1 below)

What I would like to do is (1) create two columns "start_dt" and "end_dt" using the "dt" column where if there are no gaps in the date by the patient ID then populate the start and end date with the first and last date by patient ID, however if there is a gap in service date within the patient ID then to create the separate start and end date rows per patient ID, along with (2) summing the two payment amounts by patient ID with in the one set of start and end date visits (see table 2 below).

What would be the way to run this using SQL code in SQL developer? Thank you!

Table 1:

Ptid	dt	insr_amt	op_amt
A	1/1/2021	30	20
A	1/2/2021	30	10
A	1/3/2021	30	10
A	1/4/2021	30	30
B	1/6/2021	10	10
B	1/7/2021	20	10
C	2/1/2021	15	30
C	2/2/2021	15	30
C	2/6/2021	60	30

Table 2:

Ptid	start_dt	end_dt	total_insr_amt	total_op_amt
A	1/1/2021	1/4/2021	120	70
B	1/6/2021	1/7/2021	30	20
C	2/1/2021	2/2/2021	30	60
C	2/6/2021	2/6/2021	60	30

Answer 1

You didn't mention the specific database so this solution works in PostgreSQL. You can do:

select
  ptid,
  min(dt) as start_dt,
  max(dt) as end_dt,
  sum(insr_amt) as total_insr_amt,
  sum(op_amt) as total_op_amt
from (
  select *,
    sum(inc) over(partition by ptid order by dt) as grp
  from (
    select *,
      case when dt - interval '1 day' = lag(dt) over(partition by ptid order by dt)
           then 0 else 1 end as inc
    from t
  ) x
) y
group by ptid, grp
order by ptid, grp

Result:

 ptid  start_dt    end_dt      total_insr_amt  total_op_amt 
 ----- ----------  ----------  --------------  ----------- 
 A     2021-01-01  2021-01-04  120             70           
 B     2021-01-06  2021-01-07  30              20           
 C     2021-02-01  2021-02-02  30              60           
 C     2021-02-06  2021-02-06  60              30           

See running example at DB Fiddle 1.

EDIT for Oracle

As requested, the modified query that works in Oracle is:

select
  ptid,
  min(dt) as start_dt,
  max(dt) as end_dt,
  sum(insr_amt) as total_insr_amt,
  sum(op_amt) as total_op_amt
from (
  select x.*,
    sum(inc) over(partition by ptid order by dt) as grp
  from (
    select t.*,
      case when dt - 1 = lag(dt) over(partition by ptid order by dt)
           then 0 else 1 end as inc
    from t
  ) x
) y
group by ptid, grp
order by ptid, grp

See running example at db<>fiddle 2.