MySQL 8.0

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CREATE TABLE company (
idcompany INT,
company_name VARCHAR(31),
PRIMARY KEY (idcompany));

CREATE TABLE clients (
idclient INT,
idcompany INT,
PRIMARY KEY (idclient),
FOREIGN KEY (idcompany) REFERENCES company(idcompany) ON DELETE CASCADE);

CREATE TABLE queries (
idclient INT,
temp INT,
FOREIGN KEY (idclient) REFERENCES clients(idclient) ON DELETE CASCADE);
INSERT INTO company VALUES (1, 'company 1'), (2, 'company 2');
INSERT INTO clients VALUES (1, 1), (2, 1), (3, 1), (4, 2), (5, 2), (6, 2);
INSERT INTO queries VALUES (1, 100), (1, 101), (2, 200), (2, 201), (3, 300), (3, 301),
(4, 400), (4, 401), (5, 500), (5, 501), (6, 600), (6, 601);
SELECT * FROM company co
INNER JOIN clients cl ON co.idcompany = cl.idcompany
INNER JOIN queries qu ON qu.idclient = cl.idclient;


idcompany
company_name
idclient
idcompany
idclient
temp


1
company 1
1
1
1
100

1
company 1
1
1
1
101

1
company 1
2
1
2
200

1
company 1
2
1
2
201

1
company 1
3
1
3
300

1
company 1
3
1
3
301

2
company 2
4
2
4
400

2
company 2
4
2
4
401

2
company 2
5
2
5
500

2
company 2
5
2
5
501

2
company 2
6
2
6
600

2
company 2
6
2
6
601


DELETE FROM company WHERE idcompany = 1;
SELECT * FROM company co
INNER JOIN clients cl ON co.idcompany = cl.idcompany
INNER JOIN queries qu ON qu.idclient = cl.idclient;


idcompany
company_name
idclient
idcompany
idclient
temp


2
company 2
4
2
4
400

2
company 2
4
2
4
401

2
company 2
5
2
5
500

2
company 2
5
2
5
501

2
company 2
6
2
6
600

2
company 2
6
2
6
601

idcompany	company_name	idclient	idcompany	idclient	temp
1	company 1	1	1	1	100
1	company 1	1	1	1	101
1	company 1	2	1	2	200
1	company 1	2	1	2	201
1	company 1	3	1	3	300
1	company 1	3	1	3	301
2	company 2	4	2	4	400
2	company 2	4	2	4	401
2	company 2	5	2	5	500
2	company 2	5	2	5	501
2	company 2	6	2	6	600
2	company 2	6	2	6	601