1. Oracle9i Developer:
PL/SQL Programming
Chapter 3
PL/SQL Processing

2. Chapter Objectives Use control structures to make decisions
Use looping structures to repeat code
Work with the GOTO statement
Manage errors with exception handlers
Address exception-handling issues, such as RAISE_APPLICATION_ERROR and propagation
Document code with comments

3. Brewbean’s Challenge

4. Control Structures IF Statements CASE Statements Basic IF IF/THEN/ELSE
IF/THEN/ELSIF/ELSE
CASE Statements
Basic CASE statement
Searched CASE statement
CASE expression

5. Simple IF Statement

6. Add the ELSE clause

7. Add ELSIF clauses

8. NOT ELSEIF

9. Can check multiple conditions
IF rec_order.state IN ('VA','PA','ME') THEN
lv_tax_num := rec_order.sub * .06;
ELSE
lv_tax_num := rec_order.sub * .04;
END IF;

10. Basic CASE Statement

11. No CASE Found Error

12. Searched CASE Statement

13. CASE Expression

14. Basic Loop

15. WHILE Loop

16. FOR Loop

17. Use Variables in FOR Loop
DECLARE
lv_upper_num NUMBER(3);
BEGIN
SELECT COUNT(idBasket)
INTO lv_upper_num
FROM bb_basket;
FOR i IN 1..lv_upper_num LOOP
DBMS_OUTPUT.PUT_LINE(i);
END LOOP;
END;

18. Reverse Option in FOR Loop
Instructs counter to start with the upper bound value and increment by –1 to the lower bound value
Example:
FOR I IN REVERSE 1..5 LOOP

19. GOTO Statement
Jumping control that instructs the program to move to another area of code to continue processing
Most developers discourage the use of GOTO as it complicates the flow of execution

20. Exception Handlers
Used to capture error conditions and handle the processing to allow the application to continue
Placed in the EXCEPTION section of a PL/SQL block
Two types of errors:
Oracle errors (Predefined and Non-Predefined)
User-defined errors
RAISE_APPLICATION_ERROR

21. Predefined Oracle Errors
Exception Name
Description
NO_DATA_FOUND
A SELECT statement in a PL/SQL block retrieves no rows or a nonexistent row of an index-by table is referenced.
TOO_MANY_ROWS
A SELECT statement in a PL/SQL block retrieves more than one row.
CASE_NOT_FOUND
No WHEN clause in the CASE statement is processed.
ZERO_DIVIDE
Attempted division by zero.
DUP_VAL_ON_INDEX
Attempted violation of a unique or primary key column constraint.

22. Predefined Error Example

23. Add Exception Handler

24. Non-Predefined Handler
Declare an exception
Associate an Oracle error
number to the exception name
Foreign key error occurs if
item lines are still in the
bb_basketitem table
Exception handler executes
if Foreign key error –2292
is raised by the DELETE

25. User-Defined Exception
Declare an exception
If no rows updated,
raise the exception
Exception handler

26. Additional Exception Concepts
WHEN OTHERS – traps all errors not specifically addressed by an exception handler and used for handling unanticipated errors
SQLCODE and SQLERRM –
Functions used to identify the error code and message especially in application testing to identify unanticipated errors

27. SQLCODE and SQLERRM
Log error information to a database table using these functions

28. RAISE_APPLICATION_ERROR
Allows developers to associate their own error number and message to an error
Can only be used with stored programs which is covered in Chapter 4

29. Exception Propagation
When an error occurs in a block, processing immediately moves to the EXCEPTION section of the block
If the block is nested, and no handlers address the error, the processing will then move to the EXCEPTION section of the enclosing block

30. Commenting Code
Add comments within code to identify code purpose and processing steps
Use /* */ to enclose a multiline comment
Use -- to add a single or partial line comment

31. Comment Examples DECLARE
ex_prod_update EXCEPTION; --For UPDATE of no rows exception
BEGIN
/* This block is used to update product descriptions
Constructed to support the Prod_desc.frm app screen
Exception raised if no rows updated */
UPDATE bb_product
SET description = 'Mill grinder with 5 grind settings!'
WHERE idProduct = 30;
--Check if any rows updated
IF SQL%NOTFOUND THEN
RAISE ex_prod_update;
END IF;
EXCEPTION
WHEN ex_prod_update THEN
DBMS_OUTPUT.PUT_LINE('Invalid product id entered');
END;

32. Summary Add conditional logic using IF and CASE statements
Repeat lines of code using Loop structures
Add error handlers in the EXCEPTION area to manage Oracle and user-defined errors
Use comments in code for documentation