36. Which type of join returns all the rows from both tables, filling in NULL values for non-matching rows?
A) LEFT JOIN
B) RIGHT JOIN
C) INNER JOIN
D) FULL JOIN
Answer: D
37. In a database, a check constraint is used to:
A) Enforce a relationship between two tables
B) Define the data types for attributes
C) Ensure that data meets specific criteria
D) Speed up data retrieval
Answer: C
38. Which SQL command is used to change the data in a database table?
A) UPDATE
B) MODIFY
C) ALTER
D) CHANGE
Answer: A
39. The process of creating a copy of a database to protect against data loss is called:
A) Cloning
B) Replication
C) Backup
D) Sharding
Answer: C
40. Which type of database model uses a graph-like structure to represent data relationships?
A) Hierarchical
B) Network
C) Relational
D) Graph
Answer: D
