Updating balance

[naresh_chauhan1]

Hello everyone ! I am working on drug inventory management app. here is my tables
1 drugs list

2. store where balance is maintained

3. prescription where drugs quantity issued to pt

guys I can’t figure out how to update the balance in store table using values from the prescription tables for individual drugs. so that timely stocks can be updated.
pls help, also suggest if there is other way around !
thank you !