In SQLite, process_table table stores inventory information. arrivals field is the tonnage arrived, and max_output_capacity is the maximum inventory tonnage. In theory, the arrivals in each day should be less than max_output_capacity, otherwise not all cargo can enter into the warehouse on the current day and the rest of the cargo should be taken on the next day.

Now we need to add a computed column named remaining_next_day to get the amount of tonnage that cannot enter the warehouse on the current day but will be entered on the next day.

Here is the SPL code:

=sqliteDB.query("select * from process_table order by day")

.derive(if((t=remaining_next_day[-1]+arrivals-max_output_capacity)>0,t,0):remaining_next_day)

derive function adds a computed column; [-1] represents the directly previous record.

Source:https://www.reddit.com/r/SQL/comments/1c865t8/query_to_calculate_the_remaining_units_to_the/