test.sql

SELECT 
    a2, b2, c2
FROM
    A
        INNER JOIN
    B ON B.a_id = A.id AND B.b1 = "Y"
	INNER JOIN
    C ON C.b_id = B.id AND C.c1 = "Z"
WHERE A.a1 = 'X';

// Experimendted on sample database [http://www.mysqltutorial.org/download/2]

SELECT 
    jobTitle, customerName, orderNumber, orderDate
FROM
    employees E
        INNER JOIN
    customers C ON E.employeeNumber = C.salesRepEmployeeNumber AND C.customerName = "Technics Stores Inc."
		INNER JOIN
    orders O ON C.customerNumber = O.customerNumber
WHERE E.jobTitle = "Sales Rep";