Multiplying two columns of same table and storing result to the third column of same table

Question

I m having a table

SALES(sno,comp_name,quantity,costperunit,totalcost)

After supplying the costperunit values, totalcost need to be calculated as "totalcost=quantity*costperunit".

I want to multiply 'quantity' and 'costperunit' columns and store the result in 'totalcost' column of same table.

I have tried this:

insert into SALES(totalcost) select quantity*costperunit as res from SALES

But It failed!

Somebody please help me in achieving this.. Thanks in Advance

Answer 1

Try updating the table

UPDATE SALES SET totalcost=quantity*costperunit

Answer 2

You need to use update.

UPDATE SALES SET totalcost=quantity*costperunit