Question

I have three fields F1,F2 & F3. The first two fields are filled with numbers. How can I automatically set the value for the third field “F3 = F1 – F2” like in Excel? Perhaps it can be done with macros?

Answer 1

Consider whether F3 must be an actual field in your table. Its value is derived from a simple computation, so you can perform that computation with a query field expression whenever you need it.

SELECT F1, F2, (F1 - F2) AS F3
FROM YourTable;

If you have a compelling reason why F3 must be a real field, you can execute an UPDATE statement to store the values.

UPDATE YourTable
SET F3 = F1 - F2;

The first approach is generally preferred because it ensures the computed F3 values will always be consistent with the current F1 and F2 values. If you don’t store F3, you needn’t change stored F3 values in response to changes in F1 and/or F2 values.