如何使用存储过程从 t-sql 表中现有的两列计算一列的值？

Question

In the below mentioned table I want to compute TotalCost as

TotalCost = Quantity * UnitPrice

How can I create a stored procedure to do so? Is it possible or not?

CREATE Table SalesTransaction
(
    SalesOrderNO int PRIMARY KEY NOT NULL,
    ProductId int FOREIGN KEY REFERENCES Product(ProductId),
    Quantity int,
    UnitPrice decimal,
    TotalCost decimal,
    DateOfSale date,
)

Answer 1

You wouldn't. Your syntax looks like SQL Server. You can just use a computed column:

alter table SalesTransaction add TotalCost as (Quantity * UnitPrice);

Voila. The column is now part of the table definition. And it is always up-to-date.

This assumes that quantity is some sort of number. But then again, your formula already assumes that, so you should fix the data model.