SQLite Forum

How can I fill a NULL with previous Data ?
Note that you also have the choice to fix your data once and then create a trigger so that NULL values are replaced automatically at INSERT time rather than at retrieval time.

That course of action would probably be more efficient since you only insert a new row once and infrequently.  If you only ever retrieve the data once, then the cost is equal but favours fixing the data at insert time the more times you intend to perform retrievals.