How to add a new value to a field which will depend of two other fields of the same registry?

Question

I have 3 columns:

grossWeight | tare | netWeight

the value of the first two fields will decide the value of the third field:

grossWeight | tare | netWeight
50            40     ?

i want the follow... grossWeight - tare = netWeight

grossWeight | tare | netWeight
50            40     10

how can i reach that with SQL ?

Answer 1

You cqn do it with something like:

update yourTable set netWeight = grossWeight - tare;

Consider to use triggers for more flexibility: when using a trigger you can configure it to be automatically excuted when grossWeight and/or tare are inserted or updated.