multiple filters vs OR , ndb query

Question

What is the difference between these queries:

1. With consequent filters:

   qry1 = Account.query() # Retrieve all Account entitites
   qry2 = qry1.filter(Account.userid >= 40) # Filter on userid >= 40
   qry3 = qry2.filter(Account.userid < 50) # Filter on userid < 50 as well
   

2. Using ndb.OR:

   qry = Article.query(ndb.OR(Account.userid >= 40,
                          Account.userid < 50))
   

3. Using ndb.AND:

   qry = Article.query(ndb.AND(Account.userid >= 40,
                           Account.userid < 50))
   

Answer 1

The first query does an AND. Thus, only the entities that match both inequalities will be returned by the query. The second query does an OR. Thus, entities that match either of the filters will be returned. For more information about ndb queries, take a look at NDB Queries.

Answer 2

Third and the First query are exactly identical. But the second query is absurd, it may end up returning all Entities in the Kind.