SQLite INTEGER(11) column behaving strangely

Question

So this is a SQLite database and the column map_id in table locations is of type INTEGER(11). I try to update all instances where map_id is 0 or -1 to NULL:

UPDATE locations SET map_id = NULL WHERE map_id = 0 OR map_id = -1

I add this query to my strongly-typed DataSet in a QueriesTableAdapter. I run this query and then fill my DataSet table locations with the underlying database data, hoping that I won't see any 0 or -1 in map_id column. Booo! I have some. I run the UPDATE query again and check the number of affected rows; it is zero. So no rows were affected by the UPDATE query, meaning there are no rows with map_id 0 or -1. Yet I see them in the fetched DataTable. What's going on here?

Answer 1

Because SQLite is typeless, one can store anything in any column and it won't complain. So what was happening in my case was that someone had stored empty string in an INTEGER type column. That's why my query was not updating those rows, even if they appeared similar to NULL cells. I have now added a check for empty string in my UPDATE query. Hope this helps someone down the road.