Sproc to Insert Into Multiple Tables

[Arthur Chan]

SCENARIO:
=========
Please consider this contrived relationship
Part ||---0< XOrderPart <0---|| Order

CREATE TABLE Order ( 
	Order_ID INT NOT NULL AUTO_INCREMENT, 
	OrderDate Date NOT NULL,
	PRIMARY KEY (Order_ID)
)   ENGINE=INNODB AUTO_INCREMENT= 3 CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
CREATE TABLE Part ( 
	Part_ID INT NOT NULL AUTO_INCREMENT, 
	UnitCost FLOAT NOT NULL,
	PRIMARY KEY (Part_ID)
)   ENGINE=INNODB AUTO_INCREMENT= 3 CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
CREATE TABLE XOrderPart ( 
	Order_ID INT NOT NULL,
	Part_ID INT NOT NULL,
	PRIMARY KEY (Order_ID, Part_ID)
	FOREIGN KEY(Order_ID) REFERENCES Order(Order_ID);
	FOREIGN KEY(Part_ID) REFERENCES Part(Part_ID);
)   ENGINE=INNODB AUTO_INCREMENT= 3 CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

PROBLEM:
=========
I want to use the last inserted ID from table Order and the max ID from Part as input parameters into table XOrderPart.
But mySQL throws error when I tried to access LAST_INSERT_ID() and MAX(Part_ID) in the same transaction block:

BEGIN
SET AUTOCOMMIT=0;
START TRANSACTION;
INSERT INTO Order (Customer_ID, OrderDate) VALUES (custId, ordDate);
@newOrderId = SELECT LAST_INSERT_ID();		// mySQL expects END here
@maxPartId = SELECT MAX(Part_ID) FROM Part;	// mySQL expects END here
INSERT INTO XOrderPart(Customer_ID, Part_ID) VALUES (@newOrderId, @maxPartId);
COMMIT;
END

I need all inserts to complete successfully or rollback everything with an error message.

QUESTIONS:
===========
(111) How do I get hold of LAST_INSERT_ID from Order to use as an input parameter in XOrders_Parts?
(222) If the first insert fails, will the transaction crash because the next insert violates foreign key constraints?

Apologies bothering you guys constantly. :)