| Oracle® PL/SQL® Interactive Workbook, Second Edition
By
Benjamin Rosenzweig, Elena Silvestrova
| | Table of Contents | |
Appendix D.
Answers to Test Your Thinking Sections |
Chapter 14 Packages| 1) | Add a procedure to the student_api package called remove_student. This procedure accepts a student_id and returns nothing. Based on the student id passed in, it removes the student from the database. If the student does not exist or there is a problem removing the student (such as a foreign key constraint violation), then let the calling program handle it. | A1:
|
CREATE OR REPLACE PACKAGE student_api AS
v_current_date DATE;
PROCEDURE discount;
FUNCTION new_instructor_id
RETURN instructor.instructor_id%TYPE;
FUNCTION total_cost_for_student
(p_student_id IN student.student_id%TYPE)
RETURN course.cost%TYPE;
PRAGMA RESTRICT_REFERENCES
(total_cost_for_student, WNDS, WNPS, RNPS);
PROCEDURE get_student_info
(p_student_id IN student.student_id%TYPE,
p_last_name OUT student.last_name%TYPE,
p_first_name OUT student.first_name%TYPE,
p_zip OUT student.zip%TYPE,
p_return_code OUT NUMBER);
PROCEDURE get_student_info
(p_last_name IN student.last_name%TYPE,
p_first_name IN student.first_name%TYPE,
p_student_id OUT student.student_id%TYPE,
p_zip OUT student.zip%TYPE,
p_return_code OUT NUMBER);
PROCEDURE remove_student
(p_studid IN student.student_id%TYPE);
END student_api;
CREATE OR REPLACE PACKAGE BODY student_api AS
PROCEDURE discount IS
CURSOR c_group_discount IS
SELECT distinct s.course_no, c.description
FROM section s, enrollment e, course c
WHERE s.section_id = e.section_id
GROUP BY s.course_no, c.description,
e.section_id, s.section_id
HAVING COUNT(*) >=8;
BEGIN
FOR r_group_discount IN c_group_discount LOOP
UPDATE course
SET cost = cost * .95
WHERE course_no = r_group_discount.course_no;
DBMS_OUTPUT.PUT_LINE
('A 5% discount has been given to'||
r_group_discount.course_no||' '||
r_group_discount.description);
END LOOP;
END discount;
FUNCTION new_instructor_id
RETURN instructor.instructor_id%TYPE
IS
v_new_instid instructor.instructor_id%TYPE;
BEGIN
SELECT INSTRUCTOR_ID_SEQ.NEXTVAL
INTO v_new_instid
FROM dual;
RETURN v_new_instid;
EXCEPTION
WHEN OTHERS THEN
DECLARE
v_sqlerrm VARCHAR2(250) :=
SUBSTR(SQLERRM,1,250);
BEGIN
RAISE_APPLICATION_ERROR
(-20003, 'Error in instructor_id: '||
v_sqlerrm);
END;
END new_instructor_id;
FUNCTION get_course_descript_private
(p_course_no course.course_no%TYPE)
RETURN course.description%TYPE
IS
v_course_descript course.description%TYPE;
BEGIN
SELECT description
INTO v_course_descript
FROM course
WHERE course_no = p_course_no;
RETURN v_course_descript;
EXCEPTION
WHEN OTHERS THEN
RETURN NULL;
END get_course_descript_private;
FUNCTION total_cost_for_student
(p_student_id IN student.student_id%TYPE)
RETURN course.cost%TYPE
AS
v_cost course.cost%TYPE;
BEGIN
SELECT sum(cost)
INTO v_cost
FROM course c, section s, enrollment e
WHERE c.course_no = c.course_no
AND e.section_id = s.section_id
AND e.student_id = p_student_id;
RETURN v_cost;
EXCEPTION
WHEN OTHERS THEN
RETURN NULL;
END total_cost_for_student;
PROCEDURE get_student_info
(p_student_id IN student.student_id%TYPE,
p_last_name OUT student.last_name%TYPE,
p_first_name OUT student.first_name%TYPE,
p_zip OUT student.zip%TYPE,
p_return_code OUT NUMBER)
IS
BEGIN
SELECT last_name, first_name, zip
INTO p_last_name, p_first_name, p_zip
FROM student
WHERE student.student_id = p_student_id;
p_return_code := 0;
EXCEPTION
WHEN NO_DATA_FOUND THEN
DBMS_OUTPUT.PUT_LINE
('Student ID is not valid.');
p_return_code := -100;
p_last_name := NULL;
p_first_name := NULL;
p_zip := NULL;
WHEN OTHERS THEN
DBMS_OUTPUT.PUT_LINE
('Error in procedure get_student_info');
END get_student_info;
PROCEDURE get_student_info
(p_last_name IN student.last_name%TYPE,
p_first_name IN student.first_name%TYPE,
p_student_id OUT student.student_id%TYPE,
p_zip OUT student.zip%TYPE,
p_return_code OUT NUMBER)
IS
BEGIN
SELECT student_id, zip
INTO p_student_id, p_zip
FROM student
WHERE UPPER(last_name) = UPPER(p_last_name)
AND UPPER(first_name) = UPPER(p_first_name);
p_return_code := 0;
EXCEPTION
WHEN NO_DATA_FOUND THEN
DBMS_OUTPUT.PUT_LINE
('Student name is not valid.');
p_return_code := -100;
p_student_id := NULL;
p_zip := NULL;
WHEN OTHERS THEN
DBMS_OUTPUT.PUT_LINE
('Error in procedure get_student_info');
END get_student_info;
PROCEDURE remove_student
(p_studid IN student.student_id%TYPE)
IS
BEGIN
DELETE
FROM STUDENT
WHERE student_id = p_studid;
END;
BEGIN
SELECT trunc(sysdate, 'DD')
INTO v_current_date
FROM dual;
END student_api;
| | 2) | Alter remove_student in the student_api package body to accept an additional parameter. This new parameter is a VARCHAR2 and is called p_ri. Make p_ri default to "R." The new parameter may contain a value of "R" or "C." If "R" is received, it represents DELETE RESTRICT and the procedure acts as it does now. If there are enrollments for the student, the delete is disallowed. If a "C" is received, it represents DELETE CASCADE. This functionally means that the remove_student procedure locates all records for the student in all of the CTA tables and removes them from the database before attempting to remove the student from the student table. Decide how to handle the situation where the user passes in a code other than "C" or "R." | A2:
| Answer: Your answer should look similar to the following:
CREATE OR REPLACE PACKAGE student_api AS
v_current_date DATE;
PROCEDURE discount;
FUNCTION new_instructor_id
RETURN instructor.instructor_id%TYPE;
FUNCTION total_cost_for_student
(p_student_id IN student.student_id%TYPE)
RETURN course.cost%TYPE;
PRAGMA RESTRICT_REFERENCES
(total_cost_for_student, WNDS, WNPS, RNPS);
PROCEDURE get_student_info
(p_student_id IN student.student_id%TYPE,
p_last_name OUT student.last_name%TYPE,
p_first_name OUT student.first_name%TYPE,
p_zip OUT student.zip%TYPE,
p_return_code OUT NUMBER);
PROCEDURE get_student_info
(p_last_name IN student.last_name%TYPE,
p_first_name IN student.first_name%TYPE,
p_student_id OUT student.student_id%TYPE,
p_zip OUT student.zip%TYPE,
p_return_code OUT NUMBER);
PROCEDURE remove_student
(p_studid IN student.student_id%TYPE,
p_ri IN VARCHAR2 DEFAULT 'R');
END student_api;
CREATE OR REPLACE PACKAGE BODY student_api AS
PROCEDURE discount IS
CURSOR c_group_discount IS
SELECT distinct s.course_no, c.description
FROM section s, enrollment e, course c
WHERE s.section_id = e.section_id
GROUP BY s.course_no, c.description,
e.section_id, s.section_id
HAVING COUNT(*) >=8;
BEGIN
FOR r_group_discount IN c_group_discount LOOP
UPDATE course
SET cost = cost * .95
WHERE course_no = r_group_discount.course_no;
DBMS_OUTPUT.PUT_LINE
('A 5% discount has been given to'||
r_group_discount.course_no||' '||
r_group_discount.description);
END LOOP;
END discount;
FUNCTION new_instructor_id
RETURN instructor.instructor_id%TYPE
IS
v_new_instid instructor.instructor_id%TYPE;
BEGIN
SELECT INSTRUCTOR_ID_SEQ.NEXTVAL
INTO v_new_instid
FROM dual;
RETURN v_new_instid;
EXCEPTION
WHEN OTHERS THEN
DECLARE
v_sqlerrm VARCHAR2(250) :=
SUBSTR(SQLERRM,1,250);
BEGIN
RAISE_APPLICATION_ERROR
(-20003, 'Error in instructor_id: '||
v_sqlerrm);
END;
END new_instructor_id;
FUNCTION get_course_descript_private
(p_course_no course.course_no%TYPE)
RETURN course.description%TYPE
IS
v_course_descript course.description%TYPE;
BEGIN
SELECT description
INTO v_course_descript
FROM course
WHERE course_no = p_course_no;
RETURN v_course_descript;
EXCEPTION
WHEN OTHERS THEN
RETURN NULL;
END get_course_descript_private;
FUNCTION total_cost_for_student
(p_student_id IN student.student_id%TYPE)
RETURN course.cost%TYPE
IS
v_cost course.cost%TYPE;
BEGIN
SELECT sum(cost)
INTO v_cost
FROM course c, section s, enrollment e
WHERE c.course_no = c.course_no
AND e.section_id = s.section_id
AND e.student_id = p_student_id;
RETURN v_cost;
EXCEPTION
WHEN OTHERS THEN
RETURN NULL;
END total_cost_for_student;
PROCEDURE get_student_info
(p_student_id IN student.student_id%TYPE,
p_last_name OUT student.last_name%TYPE,
p_first_name OUT student.first_name%TYPE,
p_zip OUT student.zip%TYPE,
p_return_code OUT NUMBER)
IS
BEGIN
SELECT last_name, first_name, zip
INTO p_last_name, p_first_name, p_zip
FROM student
WHERE student.student_id = p_student_id;
p_return_code := 0;
EXCEPTION
WHEN NO_DATA_FOUND THEN
DBMS_OUTPUT.PUT_LINE ('Student ID is not valid.');
p_return_code := -100;
p_last_name := NULL;
p_first_name := NULL;
p_zip := NULL;
WHEN OTHERS THEN
DBMS_OUTPUT.PUT_LINE
('Error in procedure get_student_info');
END get_student_info;
PROCEDURE get_student_info
(p_last_name IN student.last_name%TYPE,
p_first_name IN student.first_name%TYPE,
p_student_id OUT student.student_id%TYPE,
p_zip OUT student.zip%TYPE,
p_return_code OUT NUMBER)
IS
BEGIN
SELECT student_id, zip
INTO p_student_id, p_zip
FROM student
WHERE UPPER(last_name) = UPPER(p_last_name)
AND UPPER(first_name) = UPPER(p_first_name);
p_return_code := 0;
EXCEPTION
WHEN NO_DATA_FOUND THEN
DBMS_OUTPUT.PUT_LINE
('Student name is not valid.');
p_return_code := -100;
p_student_id := NULL;
p_zip := NULL;
WHEN OTHERS THEN
DBMS_OUTPUT.PUT_LINE
('Error in procedure get_student_info');
END get_student_info;
PROCEDURE remove_student
-- the parameters student_id and p_ri give user an
-- option of cascade delete or restrict delete for
-- the given students records
(p_studid IN student.student_id%TYPE,
p_ri IN VARCHAR2 DEFAULT 'R')
IS
-- declare exceptions for use in procedure
enrollment_present EXCEPTION;
bad_pri EXCEPTION;
BEGIN
-- R value is for restrict delete option
IF p_ri = 'R' THEN
DECLARE
-- a variable is needed to test if the student
-- is in the enrollment table
v_dummy CHAR(1);
BEGIN
-- This is a standard existence check
-- If v_dummy is assigned a value via the
-- SELECT INTO, the exception
-- enrollment_present will be raised
-- If the v_dummy is not assigned a value, the
-- exception no_data_found will be raised
SELECT NULL
INTO v_dummy
FROM enrollment e
WHERE e.student_id = p_studid
AND ROWNUM = 1;
-- The rownum set to 1 prevents the SELECT
-- INTO statement raise to_many_rows
-- exception
-- If there is at least one row in enrollment
-- table with corresponding student_id, the
-- restrict delete parameter will disallow the
-- deletion of the student by raising
-- the enrollment_present exception
RAISE enrollment_present;
EXCEPTION
WHEN NO_DATA_FOUND THEN
-- The no_data_found exception is raised
-- when there are no students found in the
-- enrollment table Since the p_ri indicates
-- a restrict delete user choice the delete
-- operation is permitted
DELETE FROM student
WHERE student_id = p_studid;
END;
-- when the user enter "C" for the p_ri
-- he/she indicates a cascade delete choice
ELSIF p_ri = 'C' THEN
-- delete the student form the enrollment and
-- grade tables
DELETE
FROM enrollment
WHERE student_id = p_studid;
DELETE
FROM grade
WHERE student_id = p_studid;
-- delete from student table only after
corresponding
-- records have been removed from the other
tables because
-- the student table is the parent table
DELETE
FROM student
WHERE student_id = p_studid;
ELSE
RAISE bad_pri;
END IF;
EXCEPTION
WHEN bad_pri THEN
RAISE_APPLICATION_ERROR
(-20231, 'An incorrect p_ri value was '||
'entered. The remove_student procedure can '||
'only accept a C or R for the p_ri
parameter.');
WHEN enrollment_present THEN
RAISE_APPLICATION_ERROR
(-20239, 'The student with ID'||p_studid||
' exists in the enrollment table thus records'||
' will not be removed.');
END remove_student;
BEGIN
SELECT trunc(sysdate, 'DD')
INTO v_current_date
FROM dual;
END student_api;
|
|
|
| |
No comments:
Post a Comment