multiplying values in oracle

How can I write into my sql script ORDERTOTAL is equal to wineorder.quantity * winelist.winename WHERE winelist. winename=wineinvoice.winename


CREATE TABLE "WINEINVOICE"
( "INVOICENO" NUMBER,
"ORDERID" NUMBER NOT NULL ENABLE,
"INVOICEDATE" DATE,
"CUSTOMERNAME" VARCHAR2(50) NOT NULL ENABLE,
"WINENAME" VARCHAR2(50) NOT NULL ENABLE,
"QUANTITY" NUMBER NOT NULL ENABLE,
"ORDERTOTAL" NUMBER,
"PRICE" NUMBER NOT NULL ENABLE,
CONSTRAINT "WINEINVOICE_PK" PRIMARY KEY ("INVOICENO") ENABLE,
CONSTRAINT "INVOICEORDER" FOREIGN KEY ("ORDERID")
REFERENCES "WINEORDER" ("ORDERID") ENABLE
)
/

Usually I use two tables, one for the general data of the invoice ("INVOICENO", "ORDERID", "INVOICEDATE", "CUSTOMERNAME") and another one for the invoice details ("INVOICENO", "WINENAME", "QUANTITY") and I compute totals for each invoice with a view, something like:
select "INVOICENO", "ORDERID", "INVOICEDATE", "CUSTOMERNAME", sum("WINENAME" * "QUANTITY") from "invoice", "invoice details" where invoice.invoiceno = invoice details.invoiceno
group by ...
(this is all pseudo-code).