Oracle PL/SQL and SQL Online Test

Consider the following code:

CREATE OR REPLACE FUNCTION count_users 
RETURN NUMBER 
IS 
  user_count NUMBER;
BEGIN
  SELECT COUNT(*) INTO user_count FROM users;
  RETURN user_count;
END;
/

Select the statements that are correct.

(Select all acceptable answers.)

Consider the following table definition:

CREATE TABLE couples(
  id NUMBER PRIMARY KEY NOT NULL,
  first_name VARCHAR2(50) NOT NULL,
  last_name VARCHAR2(50) NOT NULL
);

Later the following code is executed:

DECLARE
  husband_id NUMBER;
BEGIN
  SELECT id INTO husband_id FROM couples WHERE first_name = 'John' AND last_name = 'Johnson';
  INSERT INTO couples(id, first_name, last_name) VALUES(husband_id + 1, 'Jane', 'Johnson');
END;

Select the exceptions that might be raised.

(Select all acceptable answers.)

Given the following data definition, write a query that returns the number of students whose first name is John. String comparisons should be case sensitive.

TABLE students
   id INTEGER PRIMARY KEY,
   firstName VARCHAR(30) NOT NULL,
   lastName VARCHAR(30) NOT NULL