в 13:45, 26 мая 2010

2010-05-26T13:45:19Z

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2010-05-26T09:58:21Z

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==Avoid the mutating table error.==



<source lang="sql">

SQL>
SQL> CREATE TABLE lecturer (
2 id NUMBER(5) PRIMARY KEY,
3 first_name VARCHAR2(20),
4 last_name VARCHAR2(20),
5 major VARCHAR2(30),
6 current_credits NUMBER(3)
7 );
Table created.
SQL>
SQL> INSERT INTO lecturer (id, first_name, last_name, major,current_credits)
2 VALUES (10001, "Scott", "Lawson","Computer Science", 11);
1 row created.
SQL>
SQL> INSERT INTO lecturer (id, first_name, last_name, major, current_credits)
2 VALUES (10002, "Mar", "Wells","History", 4);
1 row created.
SQL>
SQL> INSERT INTO lecturer (id, first_name, last_name, major,current_credits)
2 VALUES (10003, "Jone", "Bliss","Computer Science", 8);
1 row created.
SQL>
SQL> INSERT INTO lecturer (id, first_name, last_name, major,current_credits)
2 VALUES (10004, "Man", "Kyte","Economics", 8);
1 row created.
SQL>
SQL> INSERT INTO lecturer (id, first_name, last_name, major,current_credits)
2 VALUES (10005, "Pat", "Poll","History", 4);
1 row created.
SQL>
SQL> INSERT INTO lecturer (id, first_name, last_name, major,current_credits)
2 VALUES (10006, "Tim", "Viper","History", 4);
1 row created.
SQL>
SQL> INSERT INTO lecturer (id, first_name, last_name, major,current_credits)
2 VALUES (10007, "Barbara", "Blues","Economics", 7);
1 row created.
SQL>
SQL> INSERT INTO lecturer (id, first_name, last_name, major,current_credits)
2 VALUES (10008, "David", "Large","Music", 4);
1 row created.
SQL>
SQL> INSERT INTO lecturer (id, first_name, last_name, major,current_credits)
2 VALUES (10009, "Chris", "Elegant","Nutrition", 8);
1 row created.
SQL>
SQL> INSERT INTO lecturer (id, first_name, last_name, major,current_credits)
2 VALUES (10010, "Rose", "Bond","Music", 7);
1 row created.
SQL>
SQL> INSERT INTO lecturer (id, first_name, last_name, major,current_credits)
2 VALUES (10011, "Rita", "Johnson","Nutrition", 8);
1 row created.
SQL>
SQL> INSERT INTO lecturer (id, first_name, last_name, major,current_credits)
2 VALUES (10012, "Sharon", "Clear","Computer Science", 3);
1 row created.
SQL>
SQL>
SQL> CREATE OR REPLACE PACKAGE StudentData AS
2 TYPE t_Majors IS TABLE OF lecturer.major%TYPE
3 INDEX BY BINARY_INTEGER;
4 TYPE t_IDs IS TABLE OF lecturer.ID%TYPE
5 INDEX BY BINARY_INTEGER;
6
7 myLecturerMajors t_Majors;
8 myLecturerIDs t_IDs;
9 v_NumEntries BINARY_INTEGER := 0;
10 END StudentData;
11 /
Package created.
SQL>
SQL> CREATE OR REPLACE TRIGGER RLimitMajors
2 BEFORE INSERT OR UPDATE OF major ON lecturer
3 FOR EACH ROW
4 BEGIN
5 StudentData.v_NumEntries := StudentData.v_NumEntries + 1;
6 StudentData.myLecturerMajors(StudentData.v_NumEntries) :=
7 :new.major;
8 StudentData.myLecturerIDs(StudentData.v_NumEntries) := :new.id;
9 END RLimitMajors;
10 /
Trigger created.
SQL>
SQL> CREATE OR REPLACE TRIGGER SLimitMajors
2 AFTER INSERT OR UPDATE OF major ON lecturer
3 DECLARE
4 studentMax CONSTANT NUMBER := 5;
5 studentCount NUMBER;
6 myLecturerID lecturer.ID%TYPE;
7 v_Major lecturer.major%TYPE;
8 BEGIN
9 FOR v_LoopIndex IN 1..StudentData.v_NumEntries LOOP
10 myLecturerID := StudentData.myLecturerIDs(v_LoopIndex);
11 v_Major := StudentData.myLecturerMajors(v_LoopIndex);
12
13 SELECT COUNT(*)
14 INTO studentCount
15 FROM lecturer
16 WHERE major = v_Major;
17
18 IF studentCount > studentMax THEN
19 RAISE_APPLICATION_ERROR(-20000,
20 "Too many lecturer for major " || v_Major ||
21 " because of student " || myLecturerID);
22 END IF;
23 END LOOP;
24
25 StudentData.v_NumEntries := 0;
26 END SLimitMajors;
27 /
Trigger created.
SQL>
SQL> UPDATE lecturer
2 SET major = "History"
3 WHERE ID = 10003;
1 row updated.
SQL>
SQL> UPDATE lecturer
2 SET major = "History"
3 WHERE ID = 10002;
1 row updated.
SQL>
SQL> UPDATE lecturer
2 SET major = "History"
3 WHERE ID = 10009;
1 row updated.
SQL>
SQL>
SQL> drop table lecturer;
Table dropped.
SQL>
</source>

==Order of trigger firing.==



<source lang="sql">

SQL>
SQL> CREATE TABLE session (
2 department CHAR(3),
3 course NUMBER(3),
4 description VARCHAR2(2000),
5 max_lecturer NUMBER(3),
6 current_lecturer NUMBER(3),
7 num_credits NUMBER(1),
8 room_id NUMBER(5)
9 );
Table created.
SQL>
SQL> INSERT INTO session(department, course, description, max_lecturer, current_lecturer, num_credits, room_id)
2 VALUES ("HIS", 101, "History 101", 30, 11, 4, 20000);
1 row created.
SQL>
SQL> INSERT INTO session(department, course, description, max_lecturer, current_lecturer, num_credits, room_id)
2 VALUES ("HIS", 301, "History 301", 30, 0, 4, 20004);
1 row created.
SQL>
SQL> INSERT INTO session(department, course, description, max_lecturer, current_lecturer, num_credits, room_id)
2 VALUES ("CS", 101, "Computer Science 101", 50, 0, 4, 20001);
1 row created.
SQL>
SQL> INSERT INTO session(department, course, description, max_lecturer, current_lecturer, num_credits, room_id)
2 VALUES ("ECN", 203, "Economics 203", 15, 0, 3, 20002);
1 row created.
SQL>
SQL> INSERT INTO session(department, course, description, max_lecturer, current_lecturer, num_credits, room_id)
2 VALUES ("CS", 102, "Computer Science 102", 35, 3, 4, 20003);
1 row created.
SQL>
SQL> INSERT INTO session(department, course, description, max_lecturer, current_lecturer, num_credits, room_id)
2 VALUES ("MUS", 410, "Music 410", 5, 4, 3, 20005);
1 row created.
SQL>
SQL> INSERT INTO session(department, course, description, max_lecturer, current_lecturer, num_credits, room_id)
2 VALUES ("ECN", 101, "Economics 101", 50, 0, 4, 20007);
1 row created.
SQL>
SQL> INSERT INTO session(department, course, description, max_lecturer, current_lecturer, num_credits, room_id)
2 VALUES ("NUT", 307, "Nutrition 307", 20, 2, 4, 20008);
1 row created.
SQL>
SQL> INSERT INTO session(department, course, description, max_lecturer, current_lecturer, num_credits, room_id)
2 VALUES ("MUS", 100, "Music 100", 100, 0, 3, NULL);
1 row created.
SQL>
SQL>
SQL>
SQL> CREATE TABLE MyTable (
2 num_col NUMBER,
3 char_col VARCHAR2(60)
4 );
Table created.
SQL>
SQL>
SQL> CREATE SEQUENCE trig_seq
2 START WITH 1
3 INCREMENT BY 1;
Sequence created.
SQL>
SQL> CREATE OR REPLACE PACKAGE TrigPackage AS
2 v_Counter NUMBER;
3 END TrigPackage;
4 /
Package created.
SQL>
SQL> CREATE OR REPLACE TRIGGER sessionBeforeUpdate
2 BEFORE UPDATE ON session
3 BEGIN
4 TrigPackage.v_Counter := 0;
5
6 INSERT INTO MyTable (num_col, char_col)
7 VALUES (trig_seq.NEXTVAL,
8 "Before Statement: counter = " || TrigPackage.v_Counter);
9
10 TrigPackage.v_Counter := TrigPackage.v_Counter + 1;
11 END sessionBeforeUpdate;
12 /
Trigger created.
SQL>
SQL> CREATE OR REPLACE TRIGGER sessionAfterStatement1
2 AFTER UPDATE ON session
3 BEGIN
4 INSERT INTO MyTable (num_col, char_col)
5 VALUES (trig_seq.NEXTVAL,
6 "After Statement 1: counter = " || TrigPackage.v_Counter);
7
8 TrigPackage.v_Counter := TrigPackage.v_Counter + 1;
9 END sessionAfterStatement1;
10 /
Trigger created.
SQL>
SQL> CREATE OR REPLACE TRIGGER sessionAfterStatement2
2 AFTER UPDATE ON session
3 BEGIN
4 INSERT INTO MyTable (num_col, char_col)
5 VALUES (trig_seq.NEXTVAL,"After Statement 2: counter = " || TrigPackage.v_Counter);
6
7 TrigPackage.v_Counter := TrigPackage.v_Counter + 1;
8 END sessionAfterStatement2;
9 /
Trigger created.
SQL>
SQL> CREATE OR REPLACE TRIGGER sessionBeforeRow1
2 BEFORE UPDATE ON session
3 FOR EACH ROW
4 BEGIN
5 INSERT INTO MyTable (num_col, char_col)
6 VALUES (trig_seq.NEXTVAL,
7 "Before Row 1: counter = " || TrigPackage.v_Counter);
8
9 -- Increment for the next trigger.
10 TrigPackage.v_Counter := TrigPackage.v_Counter + 1;
11 END sessionBeforeRow1;
12 /
Trigger created.
SQL>
SQL> CREATE OR REPLACE TRIGGER sessionBeforeRow2
2 BEFORE UPDATE ON session
3 FOR EACH ROW
4 BEGIN
5 INSERT INTO MyTable (num_col, char_col)
6 VALUES (trig_seq.NEXTVAL,
7 "Before Row 2: counter = " || TrigPackage.v_Counter);
8
9 TrigPackage.v_Counter := TrigPackage.v_Counter + 1;
10 END sessionBeforeRow2;
11 /
Trigger created.
SQL>
SQL> CREATE OR REPLACE TRIGGER sessionBeforeRow3
2 BEFORE UPDATE ON session
3 FOR EACH ROW
4 BEGIN
5 INSERT INTO MyTable (num_col, char_col)
6 VALUES (trig_seq.NEXTVAL,
7 "Before Row 3: counter = " || TrigPackage.v_Counter);
8
9 TrigPackage.v_Counter := TrigPackage.v_Counter + 1;
10 END sessionBeforeRow3;
11 /
Trigger created.
SQL>
SQL> CREATE OR REPLACE TRIGGER sessionAfterRow
2 AFTER UPDATE ON session
3 FOR EACH ROW
4 BEGIN
5 INSERT INTO MyTable (num_col, char_col)
6 VALUES (trig_seq.NEXTVAL,
7 "After Row: counter = " || TrigPackage.v_Counter);
8
9 TrigPackage.v_Counter := TrigPackage.v_Counter + 1;
10 END sessionAfterRow;
11 /
Trigger created.
SQL>
SQL> DELETE FROM MyTable;
0 rows deleted.
SQL>
SQL> UPDATE session
2 SET num_credits = 4
3 WHERE department IN ("HIS", "CS");
4 rows updated.
SQL>
SQL> SELECT *
2 FROM MyTable
3 ORDER BY num_col;
NUM_COL CHAR_COL
---------- ------------------------------------------------------------
1 Before Statement: counter = 0
2 Before Row 3: counter = 1
3 Before Row 2: counter = 2
4 Before Row 1: counter = 3
5 After Row: counter = 4
6 Before Row 3: counter = 5
7 Before Row 2: counter = 6
8 Before Row 1: counter = 7
9 After Row: counter = 8
10 Before Row 3: counter = 9
11 Before Row 2: counter = 10
NUM_COL CHAR_COL
---------- ------------------------------------------------------------
12 Before Row 1: counter = 11
13 After Row: counter = 12
14 Before Row 3: counter = 13
15 Before Row 2: counter = 14
16 Before Row 1: counter = 15
17 After Row: counter = 16
18 After Statement 2: counter = 17
19 After Statement 1: counter = 18
19 rows selected.
SQL>
SQL>
SQL> DROP SEQUENCE trig_seq;
Sequence dropped.
SQL>
SQL> drop table mytable;
Table dropped.
SQL>
SQL> drop table session;
Table dropped.
SQL>
SQL>
</source>

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Oracle PL/SQL/Trigger/Trigger Firing - История изменений

в 13:45, 26 мая 2010

Admin: 1 версия