Question

This question reflects my issue. How to do this in SQLite?

I’ve tried UPDATE with self-joins, isolating the self join in sub-query, triggers, and something similar to this. Here is an example:

UPDATE stage 
SET title = 
(
  SELECT 
    prior.title
  FROM 
    stage prior,
    stage now
  WHERE 
    prior.rownum+1 = now.rownum
)
WHERE
title is null

Answer 1

Every table in SQLite has got a pseudo-column called rowid (which can be accessible under several different names: rowid, oid, _rowid_, unless those names are assigned to other, real, columns). The rowid column is essentially a unique row identifier and you can use it as a sort criterion and/or in conditions.

The following query demonstrates how your problem can be solved with the help of rowid:

UPDATE stage
SET title = (
  SELECT title
  FROM stage AS prev
  WHERE title IS NOT NULL AND prev.rowid < stage.rowid
  ORDER BY prev.rowid DESC
  LIMIT 1
)
WHERE title IS NULL

Here’s a demo on SQL Fiddle.

You can read more about rowid in this SQLite manual.