SQLize | PHPize | SQLtest

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