Differential Update (Magic xpa 4.x)

For SQL databases, you can select Differential Update from the Update Style field property. Differential Update can minimize the problem of losing updated data.

The following example presents a problem that can occur when the Absolute Update option is selected.

There are 94 units of the item in stock (fetched from Total in Stock column), and User A updates the Total in Stock column in the order to 93 (having sold an item) and User B updates the Total in Stock column to 92 (having sold 2 items in the same sale). Loss of updated data occurs.

A differential update, however, updates the database as:

Total in Stock - (minus) 1 for one user

Total in Stock - (minus) 2 for the other user

The end value of Total in Stock is Total in Stock - (minus) 3, which in this example is 91. No loss of updated data occurs.