Proper syntax for updating a row in Android with SQLite

Ok, I have two Android projects both running the same API level. In one, to update a SQLite row I am using:

db.update(DATABASE_TABLE, updateValues, KEY_ROWID + "=" + rowId, null);

In the other I am using:

db.update(DATABASE_TABLE, updateValues, FIELD_COLLECTION_ID + "=?", new String[] {collectionId});

They both work. Except that in the second project, if I change the syntax to match the first one, (i.e. remove the question mark from the where clause and set whereArgs to null), it returns 0 rows affec开发者_StackOverflow社区ted. Is there a reason for this? Im thinking of sticking to the second syntax because apparently it reduces the possibility of SQL injection but I thought I would throw this one out there and see if anyone had a similar experience.

Also interesting is that the documentation doesn't specify what whereArgs is for, its just there: SQLiteDatabase:update()

When you remove the question mark, are you replacing it with the value of collectionId?

The second syntax means that SQLite can reuse the same cached copy of the query for any number of different values of rowId or collectionId, rather than having a completely different query each time it's invoked. Saves lots of resources.