[Redddd]

Есть три таблицы. БД - MySQL

Вот их описание:

Код:

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CREATE TABLE IF NOT EXISTS marshruti( idMarsh INT(11) UNSIGNED ZEROFILL NOT NULL AUTO_INCREMENT, NazvMarsh VARCHAR(128) NOT NULL, OpisMarsh VARCHAR(255) DEFAULT NULL, CenaMarsh DECIMAL(2, 0) UNSIGNED DEFAULT NULL,   PRIMARY KEY (idMarsh),   UNIQUE INDEX UK_marshruti (NazvMarsh (5), OpisMarsh (6)) )   CREATE TABLE IF NOT EXISTS zakazi(   `date` DATE NOT NULL, nomZak INT(11) UNSIGNED ZEROFILL NOT NULL AUTO_INCREMENT, idKlient INT(11) UNSIGNED NOT NULL, idMarsh INT(11) UNSIGNED NOT NULL, kolPut INT(11) UNSIGNED NOT NULL,   PRIMARY KEY (nomZak),   CONSTRAINT FK_zakazi_klienti_idKlient FOREIGN KEY (idKlient)   REFERENCES klienti (idKlient) ON DELETE RESTRICT ON UPDATE RESTRICT,   CONSTRAINT FK_zakazi_marshruti_idMarsh FOREIGN KEY (idMarsh)   REFERENCES marshruti (idMarsh) ON DELETE RESTRICT ON UPDATE RESTRICT )     CREATE TABLE IF NOT EXISTS otkazi(   `date` DATE NOT NULL, id INT(11) UNSIGNED ZEROFILL NOT NULL AUTO_INCREMENT, nomZak INT(11) UNSIGNED NOT NULL, kolVozvrPut INT(11) UNSIGNED NOT NULL,   PRIMARY KEY (id),   CONSTRAINT FK_otkazi_zakazi_nomZak FOREIGN KEY (nomZak)   REFERENCES zakazi (nomZak) ON DELETE RESTRICT ON UPDATE RESTRICT )

Необходимо за один запрос выяснить сколько денег потеряла фирма из-за отказов.
Дожился запрос не могу написать.

Может так:
select sum(m.CenaMarsh)
from marshruti m
join zakazi z on m.idMarsh = z.idMarsh
join otkazi o on o.nomZak = z.nomZak

Просто как-то