PLSQL==>>游标
2014-11-20 20:27
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1.记录类型：基于表的（table_based），基于游标（cursor_based），以及程序员定义的（programmer-defined）,为创建一个基于表或者基于游标的记录，可以使用%ROWTYPE属性:
DECLARE
vr_student student%ROWTYPE;
BEGIN
SELECT * INTO vr_student FROM student WHERE student_id = 156;
dbms_output.put_line(vr_student.first_name || ' ' ||
vr_student.last_name || ' has and ID of 156');
EXCEPTION
WHEN no_data_found THEN
raise_application_error(-2001,
'The Student ' || 'is not in the database');
END;
2.处理显示游标：
DECLARE
CURSOR c_student_name IS
SELECT first_name, last_name FROM student WHERE rownum <= 5;
vr_student_name c_student_name%ROWTYPE;
BEGIN
OPEN c_student_name;
LOOP
FETCH c_student_name
INTO vr_student_name;
EXIT WHEN c_student_name%NOTFOUND;
dbms_output.put_line('Student name: ' ||
vr_student_name.first_name || ' ' ||
vr_student_name.last_name);
END LOOP;
CLOSE c_student_name;
END;
3.处理用户定义的记录：
DECLARE
TYPE instructor_info IS RECORD(
first_name instructor.first_name%TYPE,
last_name instructor.last_name%TYPE,
sections NUMBER);
rv_instructor instructor_info;
BEGIN
SELECT rtrim(i.first_name), rtrim(i.last_name), COUNT(*)
INTO rv_instructor
FROM instructor i, section s
WHERE i.instructor_id = s.instructor_id
AND i.instructor_id = 102
GROUP BY i.first_name, i.last_name;
dbms_output.put_line('Instructor, ' || rv_instructor.first_name || ' ' ||
rv_instructor.last_name || ',teachees ' ||
rv_instructor.sections || ' section(s)');
EXCEPTION
WHEN OTHERS THEN
dbms_output.put_line('There is no instructor');
END;
游标属性rowcount：
DECLARE
v_city zipcode.city%TYPE;
BEGIN
SELECT city INTO v_city FROM zipcode WHERE zip = 07002;
IF SQL%ROWCOUNT = 1
THEN
dbms_output.put_line(v_city || 'has a ' || 'zipcode of 07002');
ELSIF SQL%ROWCOUNT = 0
THEN
dbms_output.put_line('The zipcode 07002 is ' ||
' not in the database');
ELSE
dbms_output.put_line('Stop harassing me');
END IF;
END;
集成所有游标属性：
DECLARE
v_sid student.student_id%TYPE;
CURSOR c_student IS
SELECT student_id FROM student WHERE student_id < 200;
BEGIN
OPEN c_student;
LOOP
FETCH c_student
INTO v_sid;
EXIT WHEN c_student%NOTFOUND;
dbms_output.put_line('STUDNET ID: ' || v_sid);
END LOOP;
CLOSE c_student;
EXCEPTION
WHEN OTHERS THEN
IF c_student%ISOPEN
THEN
CLOSE c_student;
END IF;
END;
修改版本：
DECLARE
v_sid student.student_id%TYPE;
CURSOR c_student IS
SELECT student_id FROM student WHERE student_id < 110;
BEGIN
OPEN c_student;
LOOP
FETCH c_student
INTO v_sid;
IF c_student%FOUND
THEN
dbms_output.put_line('Just FETCHED row ' ||
to_char(c_student%ROWCOUNT) ||
' Student ID: ' || v_sid);
ELSE
EXIT;
END IF;
END LOOP;
CLOSE c_student;
EXCEPTION
WHEN OTHERS THEN
IF c_student%ISOPEN
THEN
CLOSE c_student;
END IF;
END;
DECLARE
CURSOR c_student_enroll IS
SELECT s.student_id,
s.first_name,
s.last_name,
COUNT(*) enroll,
(CASE
WHEN COUNT(*) = 1 THEN
'class.'
WHEN COUNT(*) IS NULL THEN
'no classes.'
ELSE
'classes.'
END) CLASS
FROM student s, enrollment e
WHERE s.student_id = e.student_id
AND s.student_id < 110
GROUP BY s.student_id, first_name, last_name;
r_student_enroll c_student_enroll%ROWTYPE;
BEGIN
OPEN c_student_enroll;
LOOP
FETCH c_student_enroll
INTO r_student_enroll;
EXIT WHEN c_student_enroll%NOTFOUND;
dbms_output.put_line('Student INFO: ID ' ||
r_student_enroll.student_id || ' is ' ||
r_student_enroll.first_name || ' ' ||
r_student_enroll.last_name ||
' is enrolled in ' || r_student_enroll.enroll || ' ' ||
r_student_enroll.class);
END LOOP;
CLOSE c_student_enroll;
EXCEPTION
WHEN OTHERS THEN
IF c_student_enroll%ISOPEN
THEN
CLOSE c_student_enroll;
END IF;
END;
使用游标FOR循环：
DECLARE
CURSOR c_student IS
SELECT student_id, last_name, first_name
FROM student
WHERE student_id < 110;
BEGIN
FOR r_student IN c_student
LOOP
INSERT INTO table_log VALUES (r_student.last_name);
END LOOP;
END;
DECLARE
CURSOR c_group_discount IS
SELECT DISTINCT s.course_no
FROM section s, enrollment e
WHERE s.section_id = e.section_id
GROUP BY s.course_no, e.section_id, s.section_id
HAVING COUNT(*) >= 8;
BEGIN
FOR r_group_discount IN c_group_discount
LOOP
UPDATE course
SET cost = cost * 0.95
WHERE course_no = r_group_discount.course_no;
END LOOP;
END;;
2.处理嵌套的游标(1)：
DECLARE
v_zip zipcode.zip%TYPE;
v_student_flag CHAR;
CURSOR c_zip IS
SELECT zip, city, state FROM zipcode WHERE state = 'CT';
CURSOR c_student IS
SELECT first_name, last_name FROM student WHERE zip = v_zip;
BEGIN
FOR r_zip IN c_zip
LOOP
v_student_flag := 'N';
v_zip := r_zip.zip;
dbms_output.put_line(chr(10));
dbms_output.put_line('Student living in ' || r_zip.city);
FOR r_student IN c_student
LOOP
dbms_output.put_line(r_student.first_name || ' ' ||
r_student.last_name);
v_student_flag := 'Y';
END LOOP;
IF v_student_flag = 'N'
THEN
dbms_output.put_line('NO Students for this zipcode');
END IF;
END LOOP;
END;
3.处理嵌套的游标（2）:
DECLARE
v_amount course.cost%TYPE;
v_instructor_id instructor.instructor_id%TYPE;
CURSOR c_inst IS
SELECT first_
4000
name, last_name, instructor_id FROM instructor;
CURSOR c_cost IS
SELECT c.cost
FROM course c, section s, enrollment e
WHERE s.instructor_id = v_instructor_id
AND c.course_no = s.course_no
AND s.section_id = e.section_id;
BEGIN
FOR r_inst IN c_inst
LOOP
v_instructor_id := r_inst.instructor_id;
v_amount := 0;
dbms_output.put_line('Amount generated by instructor ' ||
r_inst.first_name || ' ' || r_inst.last_name || ' is ');
FOR r_cost IN c_cost
LOOP
v_amount := v_amount + nvl(r_cost.cost, 0);
END LOOP;
dbms_output.put_line(' ' || to_char(v_amount, '$999,999'));
END LOOP;
END;
练习：（1）
DECLARE
CURSOR c_course IS
SELECT course_no, description FROM course WHERE course_no < 120;
CURSOR c_enrollment(p_course_no IN course.course_no%TYPE) IS
SELECT s.section_no section_no, COUNT(*) COUNT
FROM section s, enrollment e
WHERE s.course_no = p_course_no
AND s.section_id = e.student_id
GROUP BY s.section_no;
BEGIN
FOR r_course IN c_course
LOOP
dbms_output.put_line(r_course.course_no || ' ' ||
r_course.description);
FOR r_enroll IN c_enrollment(r_course.course_no)
LOOP
dbms_output.put_line(chr(9) || 'Section: ' ||
r_enroll.section_no ||
' has an enrollment of: ' ||
r_enroll.count);
END LOOP;
END LOOP;
END;
练习：（2）
DECLARE
CURSOR c_student_enroll IS
SELECT s.student_id,
s.first_name,
s.last_name,
COUNT(*) enroll,
/*(CASE
WHEN COUNT(*) = 1 THEN
'class'
WHEN COUNT(*) IS NULL THEN
'no clasr'
ELSE
'classes'
END) CLASS*/
decode(COUNT(*), 1, 'CLASS', NULL, 'no classes.', 'classes') CLASS
FROM student s, enrollment e
WHERE s.student_id = e.student_id
AND s.student_id < 110
GROUP BY s.student_id, first_name, last_name;
r_student_enroll c_student_enroll%ROWTYPE;
BEGIN
OPEN c_student_enroll;
LOOP
FETCH c_student_enroll
INTO r_student_enroll;
EXIT WHEN c_student_enroll%NOTFOUND;
dbms_output.put_line('Student INFO: ID ' ||
r_student_enroll.student_id || ' is ' ||
r_student_enroll.first_name || ' ' ||
r_student_enroll.last_name ||
' is enrolled in ' ||
r_student_enroll.enroll || ' ' ||
r_student_enroll.class);
END LOOP;
CLOSE c_student_enroll;
EXCEPTION
WHEN OTHERS THEN
IF c_student_enroll%ISOPEN
THEN
CLOSE c_student_enroll;
END IF;
END;
DECLARE
vr_student student%ROWTYPE;
BEGIN
SELECT * INTO vr_student FROM student WHERE student_id = 156;
dbms_output.put_line(vr_student.first_name || ' ' ||
vr_student.last_name || ' has and ID of 156');
EXCEPTION
WHEN no_data_found THEN
raise_application_error(-2001,
'The Student ' || 'is not in the database');
END;
2.处理显示游标：
DECLARE
CURSOR c_student_name IS
SELECT first_name, last_name FROM student WHERE rownum <= 5;
vr_student_name c_student_name%ROWTYPE;
BEGIN
OPEN c_student_name;
LOOP
FETCH c_student_name
INTO vr_student_name;
EXIT WHEN c_student_name%NOTFOUND;
dbms_output.put_line('Student name: ' ||
vr_student_name.first_name || ' ' ||
vr_student_name.last_name);
END LOOP;
CLOSE c_student_name;
END;
3.处理用户定义的记录：
DECLARE
TYPE instructor_info IS RECORD(
first_name instructor.first_name%TYPE,
last_name instructor.last_name%TYPE,
sections NUMBER);
rv_instructor instructor_info;
BEGIN
SELECT rtrim(i.first_name), rtrim(i.last_name), COUNT(*)
INTO rv_instructor
FROM instructor i, section s
WHERE i.instructor_id = s.instructor_id
AND i.instructor_id = 102
GROUP BY i.first_name, i.last_name;
dbms_output.put_line('Instructor, ' || rv_instructor.first_name || ' ' ||
rv_instructor.last_name || ',teachees ' ||
rv_instructor.sections || ' section(s)');
EXCEPTION
WHEN OTHERS THEN
dbms_output.put_line('There is no instructor');
END;
游标属性rowcount：
DECLARE
v_city zipcode.city%TYPE;
BEGIN
SELECT city INTO v_city FROM zipcode WHERE zip = 07002;
IF SQL%ROWCOUNT = 1
THEN
dbms_output.put_line(v_city || 'has a ' || 'zipcode of 07002');
ELSIF SQL%ROWCOUNT = 0
THEN
dbms_output.put_line('The zipcode 07002 is ' ||
' not in the database');
ELSE
dbms_output.put_line('Stop harassing me');
END IF;
END;
集成所有游标属性：
DECLARE
v_sid student.student_id%TYPE;
CURSOR c_student IS
SELECT student_id FROM student WHERE student_id < 200;
BEGIN
OPEN c_student;
LOOP
FETCH c_student
INTO v_sid;
EXIT WHEN c_student%NOTFOUND;
dbms_output.put_line('STUDNET ID: ' || v_sid);
END LOOP;
CLOSE c_student;
EXCEPTION
WHEN OTHERS THEN
IF c_student%ISOPEN
THEN
CLOSE c_student;
END IF;
END;
修改版本：
DECLARE
v_sid student.student_id%TYPE;
CURSOR c_student IS
SELECT student_id FROM student WHERE student_id < 110;
BEGIN
OPEN c_student;
LOOP
FETCH c_student
INTO v_sid;
IF c_student%FOUND
THEN
dbms_output.put_line('Just FETCHED row ' ||
to_char(c_student%ROWCOUNT) ||
' Student ID: ' || v_sid);
ELSE
EXIT;
END IF;
END LOOP;
CLOSE c_student;
EXCEPTION
WHEN OTHERS THEN
IF c_student%ISOPEN
THEN
CLOSE c_student;
END IF;
END;
DECLARE
CURSOR c_student_enroll IS
SELECT s.student_id,
s.first_name,
s.last_name,
COUNT(*) enroll,
(CASE
WHEN COUNT(*) = 1 THEN
'class.'
WHEN COUNT(*) IS NULL THEN
'no classes.'
ELSE
'classes.'
END) CLASS
FROM student s, enrollment e
WHERE s.student_id = e.student_id
AND s.student_id < 110
GROUP BY s.student_id, first_name, last_name;
r_student_enroll c_student_enroll%ROWTYPE;
BEGIN
OPEN c_student_enroll;
LOOP
FETCH c_student_enroll
INTO r_student_enroll;
EXIT WHEN c_student_enroll%NOTFOUND;
dbms_output.put_line('Student INFO: ID ' ||
r_student_enroll.student_id || ' is ' ||
r_student_enroll.first_name || ' ' ||
r_student_enroll.last_name ||
' is enrolled in ' || r_student_enroll.enroll || ' ' ||
r_student_enroll.class);
END LOOP;
CLOSE c_student_enroll;
EXCEPTION
WHEN OTHERS THEN
IF c_student_enroll%ISOPEN
THEN
CLOSE c_student_enroll;
END IF;
END;
使用游标FOR循环：
DECLARE
CURSOR c_student IS
SELECT student_id, last_name, first_name
FROM student
WHERE student_id < 110;
BEGIN
FOR r_student IN c_student
LOOP
INSERT INTO table_log VALUES (r_student.last_name);
END LOOP;
END;
DECLARE
CURSOR c_group_discount IS
SELECT DISTINCT s.course_no
FROM section s, enrollment e
WHERE s.section_id = e.section_id
GROUP BY s.course_no, e.section_id, s.section_id
HAVING COUNT(*) >= 8;
BEGIN
FOR r_group_discount IN c_group_discount
LOOP
UPDATE course
SET cost = cost * 0.95
WHERE course_no = r_group_discount.course_no;
END LOOP;
END;;
2.处理嵌套的游标(1)：
DECLARE
v_zip zipcode.zip%TYPE;
v_student_flag CHAR;
CURSOR c_zip IS
SELECT zip, city, state FROM zipcode WHERE state = 'CT';
CURSOR c_student IS
SELECT first_name, last_name FROM student WHERE zip = v_zip;
BEGIN
FOR r_zip IN c_zip
LOOP
v_student_flag := 'N';
v_zip := r_zip.zip;
dbms_output.put_line(chr(10));
dbms_output.put_line('Student living in ' || r_zip.city);
FOR r_student IN c_student
LOOP
dbms_output.put_line(r_student.first_name || ' ' ||
r_student.last_name);
v_student_flag := 'Y';
END LOOP;
IF v_student_flag = 'N'
THEN
dbms_output.put_line('NO Students for this zipcode');
END IF;
END LOOP;
END;
3.处理嵌套的游标（2）:
DECLARE
v_amount course.cost%TYPE;
v_instructor_id instructor.instructor_id%TYPE;
CURSOR c_inst IS
SELECT first_
4000
name, last_name, instructor_id FROM instructor;
CURSOR c_cost IS
SELECT c.cost
FROM course c, section s, enrollment e
WHERE s.instructor_id = v_instructor_id
AND c.course_no = s.course_no
AND s.section_id = e.section_id;
BEGIN
FOR r_inst IN c_inst
LOOP
v_instructor_id := r_inst.instructor_id;
v_amount := 0;
dbms_output.put_line('Amount generated by instructor ' ||
r_inst.first_name || ' ' || r_inst.last_name || ' is ');
FOR r_cost IN c_cost
LOOP
v_amount := v_amount + nvl(r_cost.cost, 0);
END LOOP;
dbms_output.put_line(' ' || to_char(v_amount, '$999,999'));
END LOOP;
END;
练习：（1）
DECLARE
CURSOR c_course IS
SELECT course_no, description FROM course WHERE course_no < 120;
CURSOR c_enrollment(p_course_no IN course.course_no%TYPE) IS
SELECT s.section_no section_no, COUNT(*) COUNT
FROM section s, enrollment e
WHERE s.course_no = p_course_no
AND s.section_id = e.student_id
GROUP BY s.section_no;
BEGIN
FOR r_course IN c_course
LOOP
dbms_output.put_line(r_course.course_no || ' ' ||
r_course.description);
FOR r_enroll IN c_enrollment(r_course.course_no)
LOOP
dbms_output.put_line(chr(9) || 'Section: ' ||
r_enroll.section_no ||
' has an enrollment of: ' ||
r_enroll.count);
END LOOP;
END LOOP;
END;
练习：（2）
DECLARE
CURSOR c_student_enroll IS
SELECT s.student_id,
s.first_name,
s.last_name,
COUNT(*) enroll,
/*(CASE
WHEN COUNT(*) = 1 THEN
'class'
WHEN COUNT(*) IS NULL THEN
'no clasr'
ELSE
'classes'
END) CLASS*/
decode(COUNT(*), 1, 'CLASS', NULL, 'no classes.', 'classes') CLASS
FROM student s, enrollment e
WHERE s.student_id = e.student_id
AND s.student_id < 110
GROUP BY s.student_id, first_name, last_name;
r_student_enroll c_student_enroll%ROWTYPE;
BEGIN
OPEN c_student_enroll;
LOOP
FETCH c_student_enroll
INTO r_student_enroll;
EXIT WHEN c_student_enroll%NOTFOUND;
dbms_output.put_line('Student INFO: ID ' ||
r_student_enroll.student_id || ' is ' ||
r_student_enroll.first_name || ' ' ||
r_student_enroll.last_name ||
' is enrolled in ' ||
r_student_enroll.enroll || ' ' ||
r_student_enroll.class);
END LOOP;
CLOSE c_student_enroll;
EXCEPTION
WHEN OTHERS THEN
IF c_student_enroll%ISOPEN
THEN
CLOSE c_student_enroll;
END IF;
END;
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