1. Database Programming Using Oracle 11g
Error Handling and Exceptions

2. Error Handling and Exceptions
Error Handling and Exception: Exception vs Error
Compile time syntax issues are Error
Run-time errors are usually Exceptions.
Semantic error are exceptions

3. Error Handling and Exceptions
Need for Exception Handling
It is practically not possible to foresee all problematic events
Exception cause the program to terminate abnormally

4. Error Handling and Exceptions
Need for Exception Handling
Flow of program is broken and control is lost from developer view point
Even the best programmer can have bugs in code

5. Error Handling and Exceptions
Handling Exceptions
Special block in PL/SQL to handle exceptions.
Run-time error can be handled to avoid abnormal termination of program

6. Error Handling and Exceptions
How Exception Handling Work
When run-time error is generated Exception is raised.
Current flow stop.
Control is transferred to Exception block of PL/SQL

7. Error Handling and Exceptions
Type of Exceptions
Internal
Internal exceptions are define
Raised automatically

8. Error Handling and Exceptions
Type of Exceptions
User Define
User should define it
User should raise the exception

9. Error Handling and Exceptions
Formation of Built – in Exception
Three component
Exception Name
Exception unique number
Description

10. Error Handling and Exceptions
DUP_VAL_ON_INDEX
ORA-00001
Exception raised when you store duplicate value in unique constraint column.
CASE_NOT_FOUND
ORA-06592
Exception raised when no any choice case found in CASE statement as well as no ELSE clause in CASE statement.

11. Error Handling and Exceptions
Formation of Exception
Build – in Exceptions unique numbers are system generated

12. Error Handling and Exceptions
Syntax of Exception

13. Error Handling and Exceptions
Declare Section
All the declarations
Begin
Executable statements
Exception Section – One per block
Exception handling statements
End;

14. Error Handling and Exceptions
Syntax of Exception
One Exception section per block
Nested blocks can have separate exception section

15. Error Handling and Exceptions
Scope of Exception

16. Error Handling and Exceptions
Declare Section
All the declarations
Begin
Executable statements
Exception handling statements
declare – Inner block
begin
exception – local to innerblock
End;
Exception Section – Global exception
end;

17. Error Handling and Exceptions
Implementing Build-In Exception -I

18. Error Handling and Exceptions
DECLARE
stock_price NUMBER := 9.73;
net_earnings NUMBER := 0;
pe_ratio NUMBER;
BEGIN
pe_ratio := stock_price / net_earnings;
DBMS_OUTPUT.PUT_LINE('Price/earnings ratio = ' || pe_ratio);

19. Error Handling and Exceptions
WHEN ZERO_DIVIDE THEN
DBMS_OUTPUT.PUT_LINE('Company must have had zero earnings.');
pe_ratio := NULL;
WHEN OTHERS THEN
DBMS_OUTPUT.PUT_LINE('Some other kind of error occurred.');
END;

20. Error Handling and Exceptions
Implementing Build-In Exception -II

21. Error Handling and Exceptions
declare
grade varchar2(1):='H';
begin
CASE
WHEN grade = 'A' THEN dbms_output.put_line('Excellent');
WHEN grade = 'B' THEN dbms_output.put_line('Very Good');
WHEN grade = ‘C' THEN dbms_output.put_line('Fair');

22. Error Handling and Exceptions
WHEN grade = ‘D' THEN dbms_output.put_line('Poor');
END CASE;
exception
When case_not_found then
dbms_output.put_line(‘No Case match');
When others then
dbms_output.put_line ('In the exception block‘ || SQLERRM || SQLCode);
end;

23. Error Handling and Exceptions
Implementing Built-In Exception and SQL-III

24. Error Handling and Exceptions
declare
name varchar2(30):='';
begin
select ename into name from emp;
exception
when no_data_found then
dbms_output.put_line('Record not matched');

25. Error Handling and Exceptions
when DUP_VAL_ON_INDEX then
dbms_output.put_line('Unique Key Violated');
when others then
dbms_output.put_line(SQLCODE);
dbms_output.put_line(SQLERRM);
end;

26. Error Handling and Exceptions
Implementing Nested Exceptions-I

27. Error Handling and Exceptions
declare
name varchar2(30);
begin
select ename into name from emp where empno=7369;
dbms_output.put_line(name);
insert into emp (empno) values(7369);

28. Error Handling and Exceptions
dbms_output.put_line(name);
exception
when dup_val_on_index then dbms_output.put_line('Duplicated values in inner block');
when others then dbms_output.put_line('In inner block'); dbms_output.put_line(SQLCODE);
end;

29. Error Handling and Exceptions
when NO_data_found then
dbms_output.put_line('No Data Found in outer Block');
when others then
dbms_output.put_line('No Data found in outer block');
end;

30. Error Handling and Exceptions
Implementing Nested Exceptions-II

31. Error Handling and Exceptions
declare
name varchar2(30);
begin
select ename into name from emp where empno=7369;
dbms_output.put_line(name);
select ename into name from emp where empno=7338;

32. Error Handling and Exceptions
dbms_output.put_line(name);
exception
when INVALID_NUMBER then dbms_output.put_line(SQLCODE);
end;
when NO_DATA_FOUND then
dbms_output.put_line('No Data found in outer block');