1. 1Matthew P. Johnson, OCL4, CISDD CUNY, Sept 2005 OCL4 Oracle 10g: SQL & PL/SQL Session #7 Matthew P. Johnson CISDD, CUNY June, 2005

2. 2 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Agenda Triggers Transactions Oracle’s bulk loader Go over some labs Do some more labs

3. 3 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 New topic: Triggers PL/SQL programs that run automatically (are “triggered”) when a certain event occurs E.g.: on insert to some table On system start-up On delete from table Big benefit: need not be called explicitly However row in table x is deleted, the trigger gets called

4. 4 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Trigger events Trigger code may be “triggered” by many kinds of events: Oracle start-up/shut-down  Triggers may replace initialization scripts Data updates:  Delete: maybe delete related rows  Inserts  Updates: maybe make other rows consistent  Delete: maybe prevent DDL statements  Log creation of all objects, e.g.

5. 5 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Triggers Constraints state what must remain true  DBMS decides when to check Triggers are instructions to perform at explicitly specified times Three aspects:  An event (e.g., update to an attribute)  A condition (e.g., a test of that update value)  An action (the trigger’s effect) (deletion, update, insertion) When the event occurs, DBMS checks the constraint, and if it is satisfied, performs the action

6. 6 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 DML trigger options The trigger may be:  Statement-level (e.g., a DELETE WHERE statement) or  Row-level (e.g., for each row deleted) The trigger may run  BEFORE  AFTER or  INSTEAD OF the statement (in Oracle, not in others) It may be triggered by  INSERTs  UPDATEs  DELETEs

7. 7 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Trigger form CREATE [OR REPLACE] TRIGGER trigger name {BEFORE | AFTER | INSTEAD OF} {INSERT | DELETE | UPDATE | UPDATE OF column list} ON table name [FOR EACH ROW] [WHEN (...)] [DECLARE... ] BEGIN... executable statements... [EXCEPTION... ] END [trigger name]; CREATE [OR REPLACE] TRIGGER trigger name {BEFORE | AFTER | INSTEAD OF} {INSERT | DELETE | UPDATE | UPDATE OF column list} ON table name [FOR EACH ROW] [WHEN (...)] [DECLARE... ] BEGIN... executable statements... [EXCEPTION... ] END [trigger name];

8. 8 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Trigger type examples First run copy_tables.sql 1. statement_vs_row.sql  INSERT INTO to_table SELECT * FROM from_table; 2. before_vs_after.sql  INSERT INTO to_table SELECT * FROM from_table; 3. one_trigger_per_type.sql  INSERT INTO to_table VALUES (1); UPDATE to_table SET col1 = 10; DELETE to_table;

9. 9 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 DML Trigger e.g. Q: Why is this (maybe) better than client-side validation? CREATE OR REPLACE TRIGGER validate_employee_changes BEFORE INSERT OR UPDATE ON employee FOR EACH ROW BEGIN check_age (:NEW.date_of_birth); check_resume (:NEW.resume); END; CREATE OR REPLACE TRIGGER validate_employee_changes BEFORE INSERT OR UPDATE ON employee FOR EACH ROW BEGIN check_age (:NEW.date_of_birth); check_resume (:NEW.resume); END;

10. 10 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Triggers with WHEN NB: WHEN applies only to row-level triggers CREATE OR REPLACE TRIGGER check_raise AFTER UPDATE OF salary, commission ON employee FOR EACH ROW WHEN ((OLD.salary != NEW.salary OR (OLD.salary IS NULL AND NEW.salary IS NULL)) OR (OLD.commission != NEW.commission OR (OLD.commission IS NULL AND NEW.commission IS NULL))) BEGIN... END; CREATE OR REPLACE TRIGGER check_raise AFTER UPDATE OF salary, commission ON employee FOR EACH ROW WHEN ((OLD.salary != NEW.salary OR (OLD.salary IS NULL AND NEW.salary IS NULL)) OR (OLD.commission != NEW.commission OR (OLD.commission IS NULL AND NEW.commission IS NULL))) BEGIN... END;

11. 11 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Triggers with WHEN Parentheses are required Can only call built-in functions in when  Packages like DBMS_OUTPUT are not allowed CREATE OR REPLACE TRIGGER valid_when_clause BEFORE INSERT ON frame FOR EACH ROW WHEN ( TO_CHAR(SYSDATE,'HH24') BETWEEN 9 AND 17 )... CREATE OR REPLACE TRIGGER valid_when_clause BEFORE INSERT ON frame FOR EACH ROW WHEN ( TO_CHAR(SYSDATE,'HH24') BETWEEN 9 AND 17 )...

12. 12 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Simple trigger example R(id, data, last-modified)  data is a large string  Last-modified is a newly added date field Goal: whenever data is modified, update last- modified date Could modify all scripts/programs that touch this table  Bad idea Better: user a trigger CREATE TRIGGER UpdateDateTrigger AFTER UPDATE OF data ON R REFERENCING NEW ROW AS NewTuple FOR EACH ROW BEGIN NewTuple.last-modified = sysdate; END; CREATE TRIGGER UpdateDateTrigger AFTER UPDATE OF data ON R REFERENCING NEW ROW AS NewTuple FOR EACH ROW BEGIN NewTuple.last-modified = sysdate; END;

13. 13 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Multiple DML actions DML actions may be ORed together CREATE OR REPLACE TRIGGER three_for_the_price_of_one BEFORE DELETE OR INSERT OR UPDATE ON account_transaction FOR EACH ROW BEGIN IF INSERTING THEN :NEW.created_by := USER; :NEW.created_date := SYSDATE; ELSIF DELETING THEN audit_deletion(USER,SYSDATE); END; CREATE OR REPLACE TRIGGER three_for_the_price_of_one BEFORE DELETE OR INSERT OR UPDATE ON account_transaction FOR EACH ROW BEGIN IF INSERTING THEN :NEW.created_by := USER; :NEW.created_date := SYSDATE; ELSIF DELETING THEN audit_deletion(USER,SYSDATE); END; To find actual action, check:  INSERTING  DELETING  UPDATING

14. 14 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 More on UPDATING UPDATING may be called for partic. columns CREATE OR REPLACE TRIGGER validate_update BEFORE UPDATE ON account_transaction FOR EACH ROW BEGIN IF UPDATING ('ACCOUNT_NO') THEN errpkg.raise('Account number cannot be updated'); END IF; END; CREATE OR REPLACE TRIGGER validate_update BEFORE UPDATE ON account_transaction FOR EACH ROW BEGIN IF UPDATING ('ACCOUNT_NO') THEN errpkg.raise('Account number cannot be updated'); END IF; END;

15. 15 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Extended auditing example Tables: grades, grades_audit Run: grades_tables.sql, grades_audit.sql Cases: hacker changes grades, deletes others UPDATE grades SET grade = 'A+' WHERE student_id = 1 AND class_id = 101; UPDATE grades SET grade = 'A+' WHERE student_id = 1 AND class_id = 101; DELETE grades WHERE student_id = 2 AND class_id = 101; DELETE grades WHERE student_id = 2 AND class_id = 101;

16. 16 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Extended auditing example Run: grades_tables.sql, grades_audit2.sql Cases: hacker changes student or class ids UPDATE grades SET student_id = 3 WHERE student_id = 1 AND class_id = 101; UPDATE grades SET student_id = 1 WHERE student_id = 2 AND class_id = 101; UPDATE grades SET student_id = 2 WHERE student_id = 3 AND class_id = 101; UPDATE grades SET student_id = 3 WHERE student_id = 1 AND class_id = 101; UPDATE grades SET student_id = 1 WHERE student_id = 2 AND class_id = 101; UPDATE grades SET student_id = 2 WHERE student_id = 3 AND class_id = 101;

17. 17 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 DDL Triggers Respond to DDL events  Creating/dropping tables, indices, etc.  ALTER TABLE etc. General form: CREATE [OR REPLACE] TRIGGER trigger name {BEFORE | AFTER| {DDL event} ON {DATABASE | SCHEMA} DECLARE Variable declarations BEGIN... some code... END; CREATE [OR REPLACE] TRIGGER trigger name {BEFORE | AFTER| {DDL event} ON {DATABASE | SCHEMA} DECLARE Variable declarations BEGIN... some code... END;

18. 18 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 DDL trigger e.g. Town crier examples triggered by creates: uninformed_town_crier.sql informed_town_crier.sql

19. 19 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Available DDL events CREATE, ALTER, DROP, GRANT, RENAME, REVOKE, TRUNCATE DDL: any DDL event Q: Does this work?? CREATE OR REPLACE TRIGGER no_create AFTER CREATE ON SCHEMA BEGIN RAISE_APPLICATION_ERROR (-20000, 'ERROR : Objects cannot be created in the production database.'); END; CREATE OR REPLACE TRIGGER no_create AFTER CREATE ON SCHEMA BEGIN RAISE_APPLICATION_ERROR (-20000, 'ERROR : Objects cannot be created in the production database.'); END;

20. 20 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 DB Event triggers Form similar to DDL triggers: Triggering events: STARTUP, SHUTDOWN, SERVERERROR, LOGON, LOGOFF CREATE [OR REPLACE] TRIGGER trigger name {BEFORE | AFTER} {database event} ON {DATABASE | SCHEMA} DECLARE Variable declarations BEGIN... some code... END; CREATE [OR REPLACE] TRIGGER trigger name {BEFORE | AFTER} {database event} ON {DATABASE | SCHEMA} DECLARE Variable declarations BEGIN... some code... END;

21. 21 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 DB event restrictions Have BEFORE and AFTER as above, but they don’t always apply:  No BEFORE STARTUP/LOGON/SERVERERROR  No AFTER SHUTDOWN/LOGOFF

22. 22 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 DB Trigger e.g. Gather stats before shutdown: Log error messages CREATE OR REPLACE TRIGGER on_shutdown BEFORE SHUTDOWN ON DATABASE BEGIN gather_system_stats; END; CREATE OR REPLACE TRIGGER on_shutdown BEFORE SHUTDOWN ON DATABASE BEGIN gather_system_stats; END;

23. 23 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Trigger maintenance Enabling & disabling:  ALTER TRIGGER emp_after_insert DISABLE;  ALTER TRIGGER emp_after_insert ENABLE; Deleting:  DROP TRIGGER emp_after_insert; Viewing:  select trigger_name from user_triggers;  select text from user_source where name='TOWN_CRIER'; Check validity:  select object_name, status from user_objects where object_type='TRIGGER';

24. 24 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Triggers – important points Can replace old row (result of event) with new row Action may be performed before or after event Can refer to old row and new row WHEN clauses tests whether to continue Action may be performed either  For each row involved in event  Once per event Oracle does triggers as PL/SQL programs A trigger runs in the same transaction as the event triggering it

25. 25 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Elements of Triggers Timing of action execution: before, after or instead of triggering event The action can refer to both the old and new state of the database Update events may specify a particular column or set of columns A condition is specified with an optional WHEN clause The action can be performed either for  once for every tuple or  once for all the tuples that are changed by the database operation

26. 26 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Intermission Go over previous labs Begin lab… Break

27. 27 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 New-old topic: Transactions So far, have simply issued commands  Ignored xacts Recall, though: an xact is an operation/set of ops executed atomically  In one instant ACID test:  Xacts are atomic  Each xact (not each statement) must leave the DB consistent

28. 28 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Default xact behavior An xact begins upon login By default, xact lasts until logoff  Except for DDL statements  They automatically commit Examples with two views of emp…

29. 29 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Direct xact instructions At any point, may explicitly COMMIT:  SQL> COMMIT;  Saves all statements entered up to now  Begins new xact Conversely, can ROLLBACK  SQL> ROLLBACK;  Cancels all statements entered since start of xact Example: delete from emp; or delete junk;

30. 30 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Direct xact instructions Remember, DDL statements are auto- committed  They cannot be rollbacked Examples: Q: Why doesn’t rollback “work”? drop table junk; rollback; drop table junk; rollback; truncate table junk; rollback; truncate table junk; rollback;

31. 31 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Savepoints Xacts are atomic Can rollback to beginning of current xact But might want to rollback only part way Make 10 changes, make one bad change Want to: roll back to before last change Don’t have Word-like multiple undo  But do have savepoints

32. 32 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Savepoints Create a savepoint: emp example: --changes SAVEPOINT sp1; --changes SAVEPOINT sp2; --changes SAVEPOINT sp3 --changes ROLLBACK TO sp2; ROLLBACK TO sp1; --changes SAVEPOINT sp1; --changes SAVEPOINT sp2; --changes SAVEPOINT sp3 --changes ROLLBACK TO sp2; ROLLBACK TO sp1; SAVEPOINT savept_name; Can skip savepoints But can ROLLBACK only backwards Can ROLLBACK only to last COMMIT

33. 33 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 AUTOCOMMIT Finally, can turn AUTOCOMMIT on:  SQL> SET AUTOCOMMIT ON; Then each statement is auto-committed as its own xact  Not just DDL statements

34. 34 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 New topic: the bulk loader To insert data, can insert rows one at a time with INSERT INTO VALUES(<>) If data is in/can be computed from other tables, can use  INSERT INTO SELECT … Often, have text file of data Oracle’s bulk loader will parse file and insert all into the database

35. 35 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Using the bulk loader The bulk loader takes two files:  The data file  The control file, specifying how to load the data Control file form: LOAD DATA INFILE INTO TABLE FIELDS TERMINATED BY ' ' ( ) LOAD DATA INFILE INTO TABLE FIELDS TERMINATED BY ' ' ( )

36. 36 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 The control file Default data file extension:.dat Default control file extension:.ctl If APPEND is omitted, the table must be empty, else error Attribute list is comma-separated, but order doesn’t matter Separator can be multi-char LOAD DATA INFILE INTO TABLE FIELDS TERMINATED BY ' ' ( ) LOAD DATA INFILE INTO TABLE FIELDS TERMINATED BY ' ' ( )

37. 37 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 The control file Example control file: LOAD DATA INFILE test.dat INTO TABLE test FIELDS TERMINATED BY '|' (i, s) LOAD DATA INFILE test.dat INTO TABLE test FIELDS TERMINATED BY '|' (i, s)

38. 38 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 The data file Plain text file Each line  one row in the table Example data file: 1|foo 2|bar 3| baz 1|foo 2|bar 3| baz

39. 39 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Running the bulk loader The bulk loader is a command-line program sqlldr, separate from SQL*Plus: At cmd line, specify:  user/pass (pass is optional here)  the control file (which specifies data file), and  (optionally) a log file (dft ext:.log)  (optionally) a bad file (dft ext:.bad) c:\ sqlldr scott/tiger control=test log=test bad=bad

40. 40 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Data in the control file Can also merge the data and control file (onefile.ctl): The * indicates that the data is in this file LOAD DATA INFILE * INTO TABLE test FIELDS TERMINATED BY '|' (i, s) BEGINDATA 1|foo 2|bar 3| baz LOAD DATA INFILE * INTO TABLE test FIELDS TERMINATED BY '|' (i, s) BEGINDATA 1|foo 2|bar 3| baz

41. 41 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Loading dates In the control file’s attribute list, follow a data field with a date mask Date masks are case-INsensitive and include:  d- day  m - month  y - year withdates.ctl: LOAD DATA INFILE * INTO TABLE foo FIELDS TERMINATED BY '|' (i, d DATE 'dd-mm-yyyy') BEGINDATA 1|01-01-1990 2|4-1-1998 LOAD DATA INFILE * INTO TABLE foo FIELDS TERMINATED BY '|' (i, d DATE 'dd-mm-yyyy') BEGINDATA 1|01-01-1990 2|4-1-1998

42. 42 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Loading timestamps Similar to dates but includes more chars:  Mi – minutes  ss – seconds  hh – hour  hh24: 24-hour hour  ff – millisecond (fractional seconds) withtimestamps.ctl: LOAD DATA INFILE * APPEND INTO TABLE ts FIELDS TERMINATED BY ',' (s, t timestamp 'yyyymmddhh24miss.ff' ) BEGINDATA 1,20041012081522.123 1,10661012081522.321 LOAD DATA INFILE * APPEND INTO TABLE ts FIELDS TERMINATED BY ',' (s, t timestamp 'yyyymmddhh24miss.ff' ) BEGINDATA 1,20041012081522.123 1,10661012081522.321

43. 43 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Loading nulls Two adjacent separators are interpreted as a null value in the field: What if null in last field? Two options:  Put TRAILING NULLCOLS following field-term df  Append an extra field sep to end withnulls.ctl: 3||5 |2|4 1||6 ||7 3||5 |2|4 1||6 ||7 LOAD DATA INFILE * APPEND INTO TABLE nums FIELDS TERMINATED BY '|' TRAILING NULLCOLS (a,b,c) BEGINDATA 3||5 |2|4 1|2| 1|2|| LOAD DATA INFILE * APPEND INTO TABLE nums FIELDS TERMINATED BY '|' TRAILING NULLCOLS (a,b,c) BEGINDATA 3||5 |2|4 1|2| 1|2||

44. 44 Matthew P. Johnson, OCL3, CISDD CUNY, June 2005 Lecture 8… regexps Web apps/security XML Data warehousing extensions