Writing triggers of a table to automatically update another table - sql

Question

I got these tables (Oracle):
Doctors (Doctor_ID (PK),
Doctor_Name,
DoB,
Specialization)
Doctors_At_Work (Doctor_ID (PK),
The_Date (PK),
Hour_Start (PK),
Hour_Stop,
Room)
Consultations_Intervals (Doctor_ID (PK),
The_Date (PK),
Start_Hour_Consult (PK),
Stop_Hour_Consut,
Room)
OBS: A consultation last for only 30 minutes.
My task is to create the necessary triggers (insert/update/delete) of Doctors_At_Work in order to automatically update the Consultations_Intervals table.
What I did so far:
Create sequence seq_id_doctor START with 1 INCREMENT BY 1 ORDER NOCACHE;
CREATE OR REPLACE trigger t_1
BEFORE INSERT ON Doctors_At_Work FOR EACH ROW
BEGIN
:NEW.Doctor_ID:=seq_id_doctor.NextValue;
:NEW.The_Date:=CURRENT_TIMESTAMP;
:NEW.Hour_Start:=Select Extract (Hour from CURRENT_TIMESTAMP);
END;
/
CREATE OR REPLACE trigger t_2
AFTER INSERT OR UPDATE ON Consultations_Intervals FOR EACH ROW
BEGIN
INSERT INTO Consultations_Intervals VALUES
(:NEW.Doctor_ID, :NEW.The_Date, :NEW.Hour_Start, :NEW.Hour_Start +
interval '30' minute, :NEW.Room);
END;
/
What is wrong with it? How should I solve this task? (if there are other ideas)

Answer 1

All you need a simple trigger on your Doctors_At_work table. See example below:
Tables:
create table Doctors_At_Work (Doctor_ID number Primary key,
The_Date date ,
Hour_Start date ,
Hour_Stop date,
Room number);
create table Consultations_Intervals (Doctor_ID number,
The_Date date ,
Start_Hour_Consult number,
Stop_Hour_Consut number,
Room number);
Trigger:
create or replace trigger t_1
before insert or update or delete on doctors_at_work
for each row
begin
insert into consultations_intervals (doctor_id,
the_date,
start_hour_consult,
stop_hour_consut,
room)
values (:new.doctor_id,
current_timestamp,
extract (minute from current_timestamp),
extract (minute from current_timestamp),
:new.room);
end;
/
Output:
SQL> Prompt "Before trigger"
"Before trigger"
SQL> select * from Doctors_At_Work;
no rows selected
SQL> select * from Consultations_Intervals;
no rows selected
SQL> create or replace trigger t_1
before insert or update or delete on doctors_at_work
2 3 for each row
4 begin
insert into consultations_intervals (doctor_id,
5 6 the_date,
7 start_hour_consult,
8 stop
.
.
.
Trigger created.
SQL> Insert into DOCTORS_AT_WORK
(DOCTOR_ID, THE_DATE, HOUR_START, HOUR_STOP, ROOM)
Values
(2, TO_DATE('12/18/2016 00:00:00', 'MM/DD/YYYY HH24:MI:SS'), TO_DATE('12/13/2016 00:00:00', 'MM/DD/YYYY HH24:MI:SS'), TO_DATE('12/14/2016 00:00:00', 'MM/DD/YYYY HH24:MI:SS'), 12);
COMMIT;
2 3 4
1 row created.
SQL>
Commit complete.
SQL> select * from Doctors_At_Work;
DOCTOR_ID THE_DATE HOUR_STAR HOUR_STOP ROOM
---------- --------- --------- --------- ----------
2 18-DEC-16 13-DEC-16 14-DEC-16 12
SQL> select * from Consultations_Intervals;
DOCTOR_ID THE_DATE START_HOUR_CONSULT STOP_HOUR_CONSUT ROOM
---------- --------- ------------------ ---------------- ----------
2 19-DEC-16 17 17 12