Question 14 SQL statements are not case sensitive. True False A Moving to the nav Question 15 A _indicates an absent value that may exist but be unknown or that may not exist at all. OA Null value B. New value oc Empty tuple Op. Old value A Moving to the next question prevents changes to this answer. Question 16 The most commonly used operation in relational algebra for projecting a set of tuple from a relation is: OA Projection OB. Join Oc Select OD Union | 6 | 7 | 8 | 9 10 11 12 13 14 15 16 17 A Moving to the next question prevents changes to this answer. Question 17 Why use SQL? Allows users to access data in relational database management systems. Allows users to define the data in database and manipulate that data. Allows users to create and drop databases and tables. OD. All of the above Question 18 Which of the following SQL dauses is used to DELETE tuples from a database table? O A. CLEAR OB. REMOVE OC. DROP OD DELETE