Calculating 2 Colums and returning value into 3rd Colum

[psdeveloper]

I am new to mysql and have looked online, i have a table like this....
Quantity | Cost | Total_Cost ,

I want the total cost to = Quantity * Cost in the table, how do I do that.

Thanks

[scragar]

SELECT `quantity`, `cost`, (`cost`*`quantity`) AS `total` FROM tableName WHERE condition

[psdeveloper]

that look like a way to do it in php...is there a way to run automatically in mysql?

[chazzy]

the code he posted is SQL.