update and insert into table in with single query - sql

Question

table 1
id pk1 timestamp
1 a 10-jul-2019
2 h 11-mar-2019
3 k 19-jul-2019
4 j 7-n0v-2018
5 h 11-jul-2019
table 2
col start_date end_date
a 10-jul-2019
h 11-mar-2019 11-jul-2019
k 19-jul-2019
j 7-nov-2018
h 11-jul-2019
Q:> I want this process to be repeat after equal interval of time.
if a new value got enter into the table 1 then same value should enter into the table 2 but if existing values enters in table 1 then just update end date of previous same value of table 2 and add one new value with null end date into table 2 (example value H in table 1 and table 2).
we need to use only single query.
with merge we are not able to get this

Answer 1

if a new value got enter into the table 1 then same value should enter
into the table 2 but if existing values enters in table 1 then just
update end date of previous same value of table 2 and add one new
value with null end date into table 2
Your scenario need a Trigger to be created on Table1. You can put down your logic to update Table2 in the Trigger.
See below demo:
--Table1 DDL
Create table tab1 (
id number,
pk1 varchar(1),
time_stamp date
);
--Table2 DDL
create table tab2 (
col varchar(1),
start_date date,
end_date date
);
Here is Trigger on Table1
Create or replace trigger t1
before insert on tab1
for each row
begin
DECLARE
l_exists INTEGER;
BEGIN
SELECT COUNT(*)
INTO l_exists
FROM tab2
WHERE col = :new.pk1 ;
IF l_exists = 0
THEN
INSERT INTO TAB2
values
(:new.pk1,:new.time_stamp,null);
ELSE
Update tab2
set end_date = :new.time_stamp
where col = :new.pk1;
INSERT INTO TAB2
values
(:new.pk1,:new.time_stamp,null);
END IF;
END;
end;
--Execution:
insert into tab1 values (1,'a',to_date('10-jul-2019','DD-MON-YYYY'));
insert into tab1 values (2,'h',to_date('11-mar-2019','DD-MON-YYYY'));
insert into tab1 values (3,'k',to_date('19-jul-2019','DD-MON-YYYY'));
insert into tab1 values (4,'j',to_date('07-nov-2019','DD-MON-YYYY'));
insert into tab1 values (5,'h',to_date('11-jul-2019','DD-MON-YYYY'));
Commit;
SQL> select * from tab1;
ID P TIME_STAM
---------- - ---------
1 a 10-JUL-19
3 k 19-JUL-19
4 j 07-NOV-19
2 h 11-MAR-19
5 h 11-JUL-19
SQL> select * from tab2;
C START_DAT END_DATE
- --------- ---------
a 10-JUL-19
k 19-JUL-19
j 07-NOV-19
h 11-MAR-19 11-JUL-19
h 11-JUL-19