PL/SQL. Exception. When the PL/SQL engine cannot execute the PLSQL block it raise an error. Every Oracle error has an error number

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3 PL/SQL Exception When the PL/SQL engine cannot execute the PLSQL block it raise an error. Every Oracle error has an error number Exceptions must be handled by name. PL/SQL predefines some common Oracle errors as exceptions. Server raise error was handle by exception program. exception - it is a problem that may arise during the execution of program. Exception Handling is the mechanism to handle run-time malfunctions.

4 PL/SQL Exception Predefined error Non-Predefined error User-defined error One of approximately 20 errors that occur most often in PLSQL code. Any other Standard Oracle server error A condition that the developer determines is abnormal You need not declare these exceptions. They are predefined by the Oracle server and raised implicitly. Declare within the declarative section and enable the Oracle server to rasie them implicitly. Declare in the declarative section and raise explicitly.

5 PL/SQL Types of Exception Predefined exception Non predefined exceptions User defined error declare begin Exception error handle end declare variable exception; begin Exception error handle end declare variable exception begin raise variable; Exception error handle end

6 PL/SQL Predefined Exception Exception Error-code ACCESS_INTO_NULL Assign value to uninitialized object CASE_NOT_FOUND None of the choice in the CASE statement COLLECTION_IS_NULL Applying uninitialized collection method DUP_VAL_ON_INDEX Insert duplicate value in unique index INVALID_CURSOR An illegal cursor operation INVALID_NUMBER Conversion of character string to number is failed. LOGIN_DENIED Username or password is invalid. NO_DATA_FOUND No rows available to select. NOT_LOGGED_ON A call without connected to database. PROGRAM_ERROR PL/SQL block has an internal error

7 PL/SQL Predefined Exception Exception Error-code ROWTYPE_MISMATCH An assignment statement have incompatible return type. SELF_IS_NULL Invoke a method without object initialized. STORAGE_ERROR PL/SQL run memory was corrupted. SUBSCRIPT_BEYOND_COUNT Nested table/varray using an index number larger than element. SUBSCRIPT_OUTSIDE_LIMIT Nested table/varray using an index number is outside legal range CURSOR_ALREADY_OPEN To Open already opened cursor. SYS_INVALID_ROWID The character string does not represent a ROWID value. TOO_MANY_ROWS Single row select return multiple rows. VALUE_ERROR An arithmetic conversion or size constraint error occurred. ZERO_DIVIDE To divide a number by Zero

8 PL/SQL Predefined Exception functions for trapping exceptions function SQLCODE SQLERRM Description Returns the numeric values for the error code. Returns the message associated with the error number. SQLCODE value Description 0 No exception encommentered 1 User-defined exceptions +100 No_DATA_FOUND exceptions. Negative number Another Oracle server error number.

9 PL/SQL Predefined Exception Predefined exceptions in PL/SQL are declared globally in a package called STANDARD, defining the PL/SQL environment. So, one does not need to declare these exceptions. Instead we can write handlers for these predefined exceptions using their standard names. declare begin Exception error handle end

10 PL/SQL Predefined Exception SQL> declare 2 sdbt_no emp.empno%type; 3 sdbt_name emp.ename%type; 4 sdbt_sal emp.sal%type; 5 begin 6 select empno, ename, sal 7 into sdbt_no, sdbt_name, sdbt_sal 8 from emp; 9 dbms_output.put_line 10 (sdbt_no ' ' sdbt_name ' ' sdbt_sal); 11 exception 12 when too_many_rows then 13 dbms_output.put_line( Fetch only one row'); 14 when no_data_found then 15 dbms_output.put_line( No data to show'); 16 when others then 17 dbms_output.put_line( Contact DBA'); 18 end; 19 / Fetch only one row PL/SQL procedure successfully completed.

11 PL/SQL Non-Predefined Exception Non-predefined Oracle server error Other PL/SQL errors (no name) Declare within the declarative section and allow the Oracle Server to raise them implicitly (automatically). declare variable exception; begin Exception error handle end

12 PL/SQL Non-Predefined Exception SQL> declare 2 sdbt_exp exception; 3 pragma exception_init(sdbt_exp,-01722); 4 begin 5 insert into emp(empno,ename,sal) 6 values('rose',21,5000); 7 exception 8 when b then 9 dbms_output.put_line( Datatype Error'); 10 end; 11 / Datatype Error PL/SQL procedure successfully completed.

13 PL/SQL User defined Exception PL/SQL user defined exception to make your own exception. PL/SQL give you control to make your own exception base on oracle rules. User define exception must be declare yourself and RAISE statement to raise explicitly. Using raise_application_error we assign errmesg Sequence to declare variable exception begin raise variable; Exception error handle end

14 PL/SQL User defined Exception SQL> declare 2 sdbt_exp exception; 3 begin 4 update emp set ename= Martin' where empno=10000; 5 if sql%notfound then 6 raise sdbt_exp; 7 end if; 8 exception 9 when sbdt_exp then 10 dbms_output.put_line( Conditional record not matched'); 11 end; 12 / Conditional record not matched PL/SQL procedure successfully completed.

15 PL/SQL User defined Exception as Procedure SQL> create or replace procedure sdbt_prn( 2 v_id number, v_name varchar2, v_sal number) 3 as 4 begin 5 if (v_sal<5000) then 6 raise_application_error 7 (-20001,'the salary must be above the 8000'); 8 else 9 insert into sdbt_tab (id, name, sal) 10 values(v_id, v_name, v_sal); 11 end if; 12 end; 13 / Procedure created. SQL> begin 2 sdbt_prn (1,'scott',2000); 3 end; 4 / begin * ERROR at line 1: ORA-20001: the salary must be above the 5000 ORA-06512: at SDBT.PCN", line 6 ORA-06512: at line 2

16 PL/SQL Trapping an Exception SQL> create table sdbt_exp_trap( 2 codd number(8), 3 emessage varchar2(100), 4 time_detail timestamp); Table created. SQL> desc sdbt_exp_trap; Name Null? Type CODD NUMBER(8) EMESSAGE VARCHAR2(100) TIME_DETAIL TIMESTAMP(6)

17 PL/SQL Trapping an Exception SQL> declare 2 a emp.empno%type; 3 b emp.ename%type; 4 c emp.sal%type; 5 e1 exp_trap.codd%type; 6 e2 exp_trap.emessage%type; 7 e3 exp_trap.time_detail%type; 8 begin 9 select empno, ename, sal into a, b, c 10 from emp where sal<3000; 11 dbms_output.put_line(a ' ' b ' ' c); 12 exception 13 when no_data_found then 14 dbms_output.put_line 15 ('the given specific value not found'); 16 when cursor_already_open then 17 dbms_output.put_line 18 ('cursor already open so close it'); 19 when others then rollback; 20 e1 :=sqlcode; 21 e2 :=sqlerrm; 22 e3 :=systimestamp; 23 insert into sdbt_exp_trap values(e1,e2,e3); 24 end; 25 / PL/SQL procedure successfully completed.

18 PL/SQL Trapping an Exception SQL> select * from sdbt_exp_trap; CODD EMESSAGE TIME_DETAIL ORA-01422: exact fetch returns more than requested number of rows 06-MAR AM

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20 PL/SQL - Trigger Trigger Is a PLSQL block associated with a table, view, schema or the database. Executed explicitly whenever a particular event take pace can be either Application trigger Fires whenever an event occurs with a particular application. Database Trigger Fires whenever a data event(dml) or system event(logon/shutdown) occurs on a schema/database. A trigger cannot be called or executed, the DBMS automatically fires the trigger as a result of a data modification to the associated table. Triggers are used to maintain the referential integrity of data by changing the data in a systematic fashion.

21 PL/SQL - Trigger Advantage of Trigger Automatically generate values Auditing information in a table by recording the changes. Automatically signaling other programs that need action Collecting maintaining statistical data. Enforcing referential integrity and business rules. Event logging and storing information on table access Generating some derived column values automatically In addition, triggers can also execute stored procedures. Imposing security authorizations Preventing invalid transactions. Synchronous replication of tables.

22 PL/SQL - Trigger Trigger Based on Timing Before after Instead of Timing Points DML triggers have four basic timing points for a single table Before statement Before Each Row After Each Row After Statement

23 PL/SQL - Trigger Trigger Types Statement level triggers Row level triggers Instead of trigger before insert before update before delete after insert after update after delete before insert on each row before update on each row before delete on each row after insert on each row after update on each row after delete on each row mainly using for complex views.

24 PL/SQL - Trigger Trigger Events Database Events : AFTER STARTUP BEFORE SHUTDOWN AFTER DB_ROLE_CHANGE AFTER SERVERERROR AFTER LOGON BEFORE LOGOFF AFTER SUSPEND DDL Events : ALTER ANALYZE ASSOCIATE STATISTICS AUDIT COMMENT CREATE DISASSOCIATE STATISTICS DROP GRANT NOAUDIT RENAME REVOKE TRUNCATE DDL

25 PL/SQL - Trigger Statement Level Trigger syntax:- create trigger <trigger_name> trigger timming trigger event on object name begin triggering body end; before, after, instead of view insert or update or delete, update of column_name table name, view

26 PL/SQL - Trigger Trigger SQL> create or replace trigger sdbt_trig1 2 before insert or update or delete 3 on emp 4 begin 5 if (to_char(sysdate,'dy') in ( SAT','SUN')) 6 then 7 raise_application_error 8 (-20998, You are allowed only official days'); 9 end if; 10 end; 11 / Trigger created. ORA-20998: You are allowed only official days ORA-06512: at "SCOTT.SDBT_TRIG1", line 4 ORA-04088: error during execution of trigger 'SCOTT.SDBT_TRIG1'

27 PL/SQL - Trigger Row level trigger Syntax create trigger <trigger_name> trigger timming trigger event on object name for each row; begin triggering body end; before, after, instead of view insert or update or delete table name

28 PL/SQL - Trigger Trigger SQL> create or replace trigger sdbt_trig2 2 before insert or update of sal on emp 3 for each row 4 begin 5 if not(:new.sal>10000) 6 then 7 raise_application_error 8 (-20025,'salary must be more then ten thousand'); 9 end if; 10 end; 11 / Trigger created.

29 PL/SQL - Trigger Trigger SQL> update emp set sal=1000 where ename='scott'; update emp set sal=1000 where ename='scott' * ERROR at line 1: ORA-20025: salary must be more then ten thousand ORA-06512: at "SCOTT.SDBT_TRIG2", line 4 ORA-04088: error during execution of trigger 'SCOTT.SDBT_TRIG2'

30 PL/SQL - Trigger Trigger SQL> create or replace trigger sdbt_upper_trig3 2 before insert or update 3 on dept 4 for each row 5 begin 6 :new.dname := upper(:new.dname); 7 :new.loc := upper(:new.loc); 8 end; 9 / Trigger created.

31 PL/SQL - Trigger Trigger SQL> insert into dept values(50,'marketing','chennai'); 1 row created. SQL> select * from dept; DEPTNO DNAME LOC 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON 50 MARKETING CHENNAI

32 PL/SQL - Trigger Enable/Disable a Trigger SQL> alter trigger sdbt_trig1 disable; Trigger altered. SQL> alter trigger sdbt_trig1 enable; Trigger altered. SQL> alter table emp disable all triggers; Table altered.

33 PL/SQL - Trigger Drop a Trigger SQL> drop trigger sdbt_trig4; Trigger dropped.

34 PL/SQL - Trigger View for Triggers dba_triggers all_triggers user_triggers SQL> select trigger_name, table_name, trigger_type, status from user_triggers; TRIGGER_NAME TABLE_NAME TRIGGER_TYPE STATUS SDBT_TRIG1 EMP BEFORE STATEMENT DISABLED SDBT_TRIG2 EMP BEFORE EACH ROW DISABLED SDBT_UPPER_TRIG3 DEPT BEFORE EACH ROW ENABLED

35 PL/SQL - Trigger Restriction to Trigger A trigger may not issue any transaction control statement(e.g. commit, rollback). The trigger body cannot declare any LONG variables. Row-level triggers may not access mutating or constraining tables. Mutating table is a table that te current trigger is watching for a modifications. Constraining table is a table that is related to a mutating table through freign key.

36 PL/SQL - Trigger Trigger Triggers Automated Sequence Trigger user login with trigger Trigger used for audit a table.

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38 PL/SQL Autonomous Transaction Autonomous Transaction Autonomous transactions allow us to leave the context of the calling transaction, perform and independent transaction and return to the calling transaction without affecting it's state. The autonomous transaction has no link to the calling transaction, so only committed data can be shared by both transactions. PL/SQL blocks supported the autonomous transactions storedprocedures and functions. local procedures and functions defined in a PL/SQL declaration block. packaged procedures and functions type methods top-level anonymous blocks.

39 PL/SQL Autonomous Transaction Autonomous Transaction SQL> create table sdbt_test( id number not null, description varchar2(30) not null); Table created. SQL> insert into sdbt_test(id, description) 2 values(1,'description for 1'); 1 row created. SQL> select * from sdbt_tab; ID DESCRIPTION 1 Description for 1 2 Description for 1 SQL> insert into sdbt_test(id, description) 2 values(2,'description for 2'); 1 row created.

40 PL/SQL Autonomous Transaction Autonomous Transaction SQL> declare 2 pragma autonomous_transaction; 3 begin 4 for i in loop 5 insert into sdbt_test(id,description) 6 values(i, 'Description for ' i); 7 end loop; 8 commit; 9 end; 10 / PL/SQL procedure successfully completed. SQL> select * from sdbt_tab; ID DESCRIPTION 1 Description for 1 2 Description for 2 3 Description for 3 4 Description for 4 5 Description for 5 6 Description for 6 7 Description for 7 8 Description for 8 9 Description for 9 10 Description for 10

41 PL/SQL Autonomous Transaction Autonomous Transaction SQL> rollback; ID DESCRIPTION Rollback complete. First 2 rows inserted by current session have been rolled back, while the rows inserted by the autonomous transaction remain. The presence of the PRAGMA AUTONOMOUS_TRANSACTION compiler directive made the anonymous block run in its own transaction, so the internal commit statement did not affect the calling session. SQL> select * from sdbt_tab; 3 Description for 3 4 Description for 4 5 Description for 5 6 Description for 6 7 Description for 7 8 Description for 8 9 Description for 9 10 Description for 10

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