SQLite Forum

Removing not null constraint doesn't behave correctly
I see.  I didn't notice the scrollbars and I was only seeing the OP's report
down through the first "PRAGMA integrity_check" and everything seemed fine
up until then.

The problem is that after an edit to the sqlite_master table, you really do
need to close and reopen the database connection so that SQLite will rebuild
its internal schema.  If you do that, the script works as desired.

I will update the documentation accordingly.