Oracle converting an INSERT to MERGE ot not EXISTS - sql

Question

I have the following code, which is working fine. If I run the procedure more than once with the same values I get a PRIMARY KEY violation, which I expect. Could the INSERT be converted into a MERGE or NOT EXISTS to avoid this issue?
The examples I saw online appear to be using literal values or an ON statement with the MERGE.
As I am a novice SQL developer any help or sample code, which reflects my requirement would be greatly appreciated.
Thanks in advance to all who answer.
ALTER SESSION SET NLS_DATE_FORMAT = 'MMDDYYYY HH24:MI:SS';
CREATE OR REPLACE TYPE nt_date IS TABLE OF DATE;
/
CREATE OR REPLACE FUNCTION generate_dates_pipelined(
p_from IN DATE,
p_to IN DATE
)
RETURN nt_date PIPELINED DETERMINISTIC
IS
v_start DATE := TRUNC(LEAST(p_from, p_to));
v_end DATE := TRUNC(GREATEST(p_from, p_to));
BEGIN
LOOP
PIPE ROW (v_start);
EXIT WHEN v_start >= v_end;
v_start := v_start + INTERVAL '1' DAY;
END LOOP;
RETURN;
END generate_dates_pipelined;
/
create table schedule_assignment(
schedule_id number(4),
schedule_date DATE,
employee_id NUMBER(6) DEFAULT 0,
constraint sa_chk check (schedule_date=trunc(schedule_date, 'dd')),
constraint sa_pk primary key (schedule_id, schedule_date)
);
CREATE OR REPLACE PROCEDURE
create_schedule_assignment (
p_schedule_id IN NUMBER,
p_start_date IN DATE,
p_end_date IN DATE
)
IS
BEGIN
INSERT INTO schedule_assignment(
schedule_id,
schedule_date
)
SELECT
p_schedule_id,
COLUMN_VALUE
FROM TABLE(generate_dates_pipelined(p_start_date, p_end_date));
END;
EXEC create_schedule_assignment (1, DATE '2021-08-21', DATE '2021-08-30');

Answer 1

Rewrite procedure to
SQL> CREATE OR REPLACE PROCEDURE
2 create_schedule_assignment (
3 p_schedule_id IN NUMBER,
4 p_start_date IN DATE,
5 p_end_date IN DATE
6 )
7 IS
8 BEGIN
9 merge into schedule_assignment s
10 using (select p_schedule_id as schedule_id,
11 column_value as schedule_date
12 from table(generate_dates_pipelined(p_start_date, p_end_date))
13 ) x
14 on ( x.schedule_id = s.schedule_id
15 and x.schedule_date = s.schedule_date
16 )
17 when not matched then insert (schedule_id, schedule_date)
18 values (x.schedule_id, x.schedule_date);
19 END;
20 /
Procedure created.
SQL>
Testing: initially, table is empty:
SQL> select schedule_id, min(schedule_date) mindat, max(schedule_date) maxdate, count(*)
2 from schedule_assignment group by schedule_id;
no rows selected
Run the procedure for the 1st time:
SQL> EXEC create_schedule_assignment (1, DATE '2021-08-21', DATE '2021-08-30');
PL/SQL procedure successfully completed.
Table contents:
SQL> select schedule_id, min(schedule_date) mindat, max(schedule_date) maxdate, count(*)
2 from schedule_assignment group by schedule_id;
SCHEDULE_ID MINDAT MAXDATE COUNT(*)
----------- ---------- ---------- ----------
1 21/08/2021 30/08/2021 10
Run the procedure with same parameters again:
SQL> EXEC create_schedule_assignment (1, DATE '2021-08-21', DATE '2021-08-30');
PL/SQL procedure successfully completed.
SQL> EXEC create_schedule_assignment (1, DATE '2021-08-21', DATE '2021-08-30');
PL/SQL procedure successfully completed.
SQL> EXEC create_schedule_assignment (1, DATE '2021-08-21', DATE '2021-08-30');
PL/SQL procedure successfully completed.
Result: nothing changed, no rows in table (but no error either):
SQL> select schedule_id, min(schedule_date) mindat, max(schedule_date) maxdate, count(*)
2 from schedule_assignment group by schedule_id;
SCHEDULE_ID MINDAT MAXDATE COUNT(*)
----------- ---------- ---------- ----------
1 21/08/2021 30/08/2021 10
SQL>
Run the procedure with the same SCHEDULE_ID, but different dates:
SQL> EXEC create_schedule_assignment (1, DATE '2021-08-29', DATE '2021-09-02');
PL/SQL procedure successfully completed.
SQL> select schedule_id, min(schedule_date) mindat, max(schedule_date) maxdate, count(*)
2 from schedule_assignment group by schedule_id;
SCHEDULE_ID MINDAT MAXDATE COUNT(*)
----------- ---------- ---------- ----------
1 21/08/2021 02/09/2021 13
SQL>
Right; number of rows is now increased to 13 (was 10 previously, because 31.08., 01.09. and 02.09. were added).
New SCHEDULE_ID:
SQL> EXEC create_schedule_assignment (2, DATE '2021-09-05', DATE '2021-09-07');
PL/SQL procedure successfully completed.
SQL> select schedule_id, min(schedule_date) mindat, max(schedule_date) maxdate, count(*)
2 from schedule_assignment group by schedule_id;
SCHEDULE_ID MINDAT MAXDATE COUNT(*)
----------- ---------- ---------- ----------
1 21/08/2021 02/09/2021 13
2 05/09/2021 07/09/2021 3
SQL>
Looks OK to me.