Аналогично другим ответам.Но вот, пожалуйста.
Структура таблицы и данные
CREATE TABLE systemtbl
(
reg INT,
ic INT,
plate VARCHAR(255),
type VARCHAR(255)
);
CREATE TABLE ownertbl
(
name VARCHAR(255),
ic INT
);
CREATE TABLE cartbl
(
plate VARCHAR(255),
color VARCHAR(255),
year INT,
make VARCHAR(255),
model VARCHAR(255),
capacity DECIMAL(2, 1)
);
CREATE TABLE trucktbl
(
plate VARCHAR(255),
color VARCHAR(255),
year INT,
make VARCHAR(255),
model VARCHAR(255),
capacity DECIMAL(2, 1),
maxload INT
);
INSERT INTO systemtbl
VALUES (1000, 22222,'WWW123', 'car'),
(1001, 11111, 'BBB987', 'truck');
INSERT INTO ownertbl
VALUES ('john', 22222),
('joe', 11111);
INSERT INTO cartbl
VALUES ('WWW123', 'blue', 2015, 'Honda', 'City', 1.5);
INSERT INTO trucktbl
VALUES ('BBB987', 'red', 2018, 'Toyota', 'Hilux', 2.0, 3000 );
SQL-запрос
SELECT systemtbl.reg,
ownertbl.name,
systemtbl.ic,
systemtbl.plate,
systemtbl.type,
tmp.color,
tmp.year,
tmp.make,
tmp.model,
tmp.capacity,
tmp.maxload
FROM (SELECT plate, color, year, make, model, capacity, NULL AS maxload
FROM cartbl
UNION ALL
SELECT plate, color, year, make, model, capacity, maxload
FROM trucktbl) tmp
INNER JOIN systemtbl USING (plate)
INNER JOIN ownertbl USING (ic)
Вывод
+-------+-------+--------+---------+--------+--------+-------+---------+--------+-----------+---------+
| reg | name | ic | plate | type | color | year | make | model | capacity | maxload |
+-------+-------+--------+---------+--------+--------+-------+---------+--------+-----------+---------+
| 1000 | john | 22222 | WWW123 | car | blue | 2015 | Honda | City | 1.5 | (null) |
| 1001 | joe | 11111 | BBB987 | truck | red | 2018 | Toyota | Hilux | 2 | 3000 |
+-------+-------+--------+---------+--------+--------+-------+---------+--------+-----------+---------+
Онлайн-демонстрация: http://sqlfiddle.com/#!9/52596e/3/0