SQLize | PHPize | SQLtest

create table orders ( customerid int NOT NULL, orderid int NOT NULL ); create table discounts ( id int NOT NULL, value int NOT NULL ); create table customers ( id int not null, name varchar(20) not null, phone varchar(20) not null ); create table orderitems ( orderid int NOT NULL, productid int NOT NULL, discount_code int NULL ); create table products ( productid int not null, name varchar(20) not null, productprice int not null ); insert into customers values (1, "TEST NAME", "TEST PHONE"); insert into orders values (1, 1), (2, 1); insert into discounts values (1, 3), (2, 3); insert into orderitems values (1, 1, 2), (1, 1, null); insert into products values (1, "Product Name", 39); SELECT sum(if(orderitems.discount_code is not null, products.productprice - discounts.value, products.productprice)), customers.name, customers.phone FROM `customers` inner join orders on customers.id = orders.customerid inner join orderitems on orders.orderid = orderitems.orderid left join discounts on discounts.id = orderitems.discount_code inner join products on orderitems.productid = products.productid WHERE customers.id = "1";