sql - How I get computed column in select statement? -

i have 3 tables.

one product table , has unitsaleprice , other table orderproduct , has column productquantity (how order particular product) , orders add detail of customer's orders.

i wrote select statement this:

select      orderprice      product, orderproduct, orders      orderproduct.product_id = product.product_id      , orders.order_id = orderproduct.order_id     , orderprice (orderproduct.productqty * product.unitsaleprice) ; 

but orderprice column not in 3 tables , dummy column.

when run query gives error column not exists.

how do this???

you should learn use explicit join syntax:

select (op.productqty * p.unitsaleprice) orderprice product p join      orderproduct op      on op.product_id = p.product_id join      orders o      on o.order_id = op.order_id;