MC Which of the following statements describes NoSQL databases best? A NoSQL database offers no support for SQL. incorrect NoSQL databases do not support joins. incorrect NoSQL databases are non-relational. correct NoSQL databases are not capable to deal with large datasets. incorrect MC Which of the following is not an example of a NoSQL database? Graph based databases. incorrect XML based databases. incorrect Document based databases. incorrect All three can be regarded as NoSQL databases. correct MC Which of the following is not a property of a good hash function for use in key-value based storage structures? A hash function should always return the same output for the same input. incorrect A hash function should return an output of fixed size. incorrect A good hash function should map its inputs as evenly as possible over the output range. incorrect Two hashes from two inputs that differ little should also differ as little as possible. correct MC Which statement is CORRECT? The fact that most NoSQL databases adopt an eventual consistency approach is due to the CAP theorem, which states that strong consistency cannot be obtained when availability and partitioning has to be ensured. correct Replicas in a distributed NoSQL environment relate to making periodic backups of the database to a second system. incorrect Stabilization relates to the waiting time between the start-up of a NoSQL system and when the system becomes usable to receive user queries. incorrect Some relational constructs, such as the many-to-many relationship, are harder to express using graph databases. incorrect MC Which statement is CORRECT? Document stores require users to define document schemas before data can be inserted. incorrect Document stores require that you perform all filtering and aggregation logic in your application. incorrect Document stores are built on the same ideas as key-value and tuple based database systems. correct Document stores do not provide SQL-like capabilities. incorrect MC When are column oriented databases more efficient? When many columns of a single group need to be fetched at the same time. incorrect When inserts are performed where all of the row data is supplied at the same time. incorrect When aggregates need to be calculated over many or all rows in the dataset. correct When a lot of JOINs need to be performed in queries. incorrect MC Which statement is NOT CORRECT? Graphs are mathematical structures consisting of nodes and edges. incorrect Graph models are not capable to model many-to-many relationships. correct Edges in graphs can be uni- or bidirectional. incorrect Graph databases work particularly well on tree-like structures. incorrect MC What does the following Cypher query express?

OPTIONAL MATCH (user;User)-[:FRIENDS_WITH]-(friend;User)
WHERE user.name = "Bart Baesens"
RETURN user, count(friend) AS NumberOfFriends Get the node for Bart Baesens and a count of all his friends, but only if at least one FRIENDS_WITH relation exists. correct Get the node for Bart Baesens and a count of all his friends, even if no FRIENDS_WITH relation exists. incorrect This query will fail if Bart Baesens is FRIENDS_WITH himself. incorrect Get the node for Bart Baesens and all his friends. incorrect MC Using Cypher, how do you get a list of all movies Wilfried Lemahieu has liked, when he has given at least four stars? SELECT (b:User)--m:Movie)
WHERE b.name = "Wilfried Lemahieu"
AND m.starts >= 4 incorrect MATCH (b:User)-[I:LIKES]-(m:Movie)
WHERE b.name = "Wilfried Lemahieu"
AND m.stars >=4
RETURN m incorrect MATCH (b:User)-[I:LIKES]-(m:Movie)
WHERE b.name = "Wilfried Lemahieu"
AND l.stars >= 4
RETURN m correct MATCH (b:User)--(m:Movie)
WHERE b.name = "Wilfried Lemahieu"
AND l.stars >= 4
RETURN m incorrect MC What does the following Cypher query express?

MATCH (bart:User {name:'Bart'})-[:KNOWS*2]->(f)
WHERE NOT((bart)-[:KNOWS]->(f))
RETURN f
Return all of Bart's friends, and their friends as well incorrect Does not return Bart's friends, but returns their friends incorrect Does not return Bart's friends, but returns their friends if Bart does not know them correct Returns Bart's friends who have exactly one other friend incorrect