How to delete from 3 tables with one query using where exists - sql

Question

I have four tables Monitoring, Participant, Participant validation group, Validation group,
I would like to delete all monitorings, and there particpants also each particpant possibly (not always) has participant validation group.
Blockquote
but i have the error sql command not properly ended.
NOTE: I am on oracle database and inner joins would not work here.
I would like to achieve an optimized query
that could take only the application number of monitoring and delete all monitorings, participants for each monitoring and participant validation group.
I am not sure if its actually possible in a single query if its not then what could be the optimized way to do this. and I cant use jpa for this at the moment.
Expected results, both monitorings are deleted, and there particpants as well as participant validation groups

Answer 1

You can define foreign keys on child tables to "ON DELETE CASCADE". So when you delete a parent table it will delete associated rows from child tables.
create table parent (
id NUMBER(10),
value varchar2(30),
constraint parent_pk primary key (id)
);
CREATE TABLE child
( id NUMBER(10) not null,
value NUMBER(10) not null,
constraint child_pk primary key (id,value),
CONSTRAINT parent_child_fk
FOREIGN KEY (id)
REFERENCES parent(id)
ON DELETE CASCADE
);
CREATE TABLE grandchild
( id NUMBER(10) not null,
value NUMBER(10) not null,
constraint grandchild_pk primary key (id,value),
CONSTRAINT child_grandchild_fk
FOREIGN KEY (id,value)
REFERENCES child(id,value)
ON DELETE CASCADE
);
insert into parent values (1,'a');
insert into parent values (2,'b');
insert into parent values (3,'c');
insert into child values (1,1);
insert into child values (1,2);
insert into child values (1,3);
insert into child values (2,1);
insert into child values (2,2);
insert into child values (2,3);
insert into child values (3,1);
insert into child values (3,2);
insert into child values (3,3);
insert into grandchild values (1,1);
insert into grandchild values (1,2);
insert into grandchild values (1,3);
insert into grandchild values (2,1);
insert into grandchild values (2,2);
insert into grandchild values (2,3);
insert into grandchild values (3,1);
insert into grandchild values (3,2);
insert into grandchild values (3,3);
SELECT (
SELECT COUNT(*)
FROM parent
) AS parent_cnt,
(
SELECT COUNT(*)
FROM child
) AS child_cnt,
(
SELECT COUNT(*)
FROM grandchild
) AS grandchild_cnt
FROM dual
DELETE from parent where value = 'a';
SELECT (
SELECT COUNT(*)
FROM parent
) AS parent_cnt,
(
SELECT COUNT(*)
FROM child
) AS child_cnt,
(
SELECT COUNT(*)
FROM grandchild
) AS grandchild_cnt
FROM dual
PARENT_CNT CHILD_CNT GRANDCHILD_CNT
2 6 6