MySQL Sum with multiple tables

[JaneDoe]

How can I get the sum of a certain column in multiple tables? I have table A, B, C. Each table has a column Net_Sales. I want the total sum of: Net_Sales of Table A where the date is 4-1-04, Net_Sales of Table B where the date is 4-1-04, and Net_Sales of Table B where the date is 4-1-04. So, if Table A was 5, Table B was 5 and Table C was 5, then the total sum should be 15. This is what I did and obviously its wrong:

select Net_Sales,
sum(A.Net_Sales, B.Net_Sales, C.Net_Sales) as netSalesSum
from A, B, C
where Store='123456'
and Sales_Date between '2004-03-28'
and '2004-04-02'
Group by Sales_Date

[bastien]

try

select  

(sum(A.Net_Sales) +sum(B.Net_Sales) + sum(C.Net_Sales)) as netSalesSum 
from A, B, C 
where Store='123456' 
and Sales_Date between '2004-03-28' 
and '2004-04-02' 
Group by Sales_Date