The document provides a comprehensive overview of programming in Oracle using PL/SQL, detailing its procedural language features, including blocks, loops, and error handling. It describes both anonymous and named PL/SQL blocks, along with how to declare variables, use conditional logic, and create functions, procedures, and triggers. Additionally, it emphasizes the integration of SQL with programming constructs to enhance functionality and efficiency in database management.

1. Programming in Oracle
with PL/SQL
Procedural Language Extension toSQL

2. n PL/SQL
n PL/SQL Blocks
n Anonymous blocks
n Using select statement
n Using conditions
n Loops
n Printing output
n Named blocks
n Functions
n Procedures
n Triggers

3. PL/SQL
n Allows using general programming tools with
SQL, for example: loops, conditions,
functions, etc.
n This allows a lot more freedom than general
SQL, and is lighter-weight than JDBC.
n We write PL/SQL code in a regular file, for
example PL.sql, and load it with @PL in the
sqlplus console.

4. PL/SQL Blocks
n PL/SQL code is built of Blocks, with a unique
structure.
n There are two types of blocks in PL/SQL:
1. Anonymous Blocks: have no name (like scripts)
n can be written and executed immediately in SQLPLUS
n can be used in a trigger
2. Named Blocks:
n Procedures
n Functions

5. Anonymous Block Structure:
DECLARE (optional)
/* Here you declare the variables you will use in this block */
BEGIN (mandatory)
/* Here you define the executable statements (what the block
DOES!)*/
EXCEPTION (optional)
/* Here you define the actions that take place if an exception is
thrown during the run of this block */
END; (mandatory)
/
A correct completion of a block will generate the following message:
PL/SQL procedure successfully completed

6. DECLARE
Syntax
identifier [CONSTANT] datatype [NOT NULL]
[:= | DEFAULT expr];
Examples
Declare
birthday DATE;
age NUMBER(2) NOT NULL := 27;
name VARCHAR2(13) := 'Levi';
magic CONSTANT NUMBER := 77;
valid BOOLEAN NOT NULL := TRUE;

7. SELECT Statements
DECLARE
v_sname VARCHAR2(10);
v_rating NUMBER(3);
BEGIN
SELECT sname, rating
INTO v_sname, v_rating
FROM Sailors
WHERE sid = '112';
END;
/ n INTO clause is required.
n Query must return exactly one row.
n Otherwise, a NO_DATA_FOUND or
TOO_MANY_ROWS exception is thrown

8. Conditional logic
Condition: Nested conditions:
If <cond> If <cond>
then <command> then
if <cond2>
elsif <cond2>
then
then <command1>
<command2> end if;
else else <command2>
<command3> end if;
end if;

9. IF-THEN-ELSIF Statements
. . .
IF rating > 7 THEN
v_message := 'You are great';
ELSIF rating >= 5 THEN
v_message := 'Not bad';
ELSE
v_message := 'Pretty bad';
END IF;
. . .

10. Suppose we have the
following table: mylog
create table mylog( logon_nu
who m
who varchar2(30),
logon_num number Peter 3
);
n Want to keep track of how John 4
many times someone Moshe 2
logged on to the DB
n When running, if user is
already in table, increment
logon_num. Otherwise,
insert user into table

11. Solution
DECLARE
cnt NUMBER;
BEGIN
select count(*)
into cnt
from mylog
where who = user;
if cnt > 0 then
update mylog
set logon_num = logon_num + 1
where who = user;
else
insert into mylog values(user, 1);
end if;
commit;
end;
/

12. Loops: FOR Loop
DECLARE
i number_table.num%TYPE;
BEGIN
FOR i IN 1..10 LOOP
INSERT INTO number_table VALUES(i);
END LOOP;
END;
Notice that i is incremented
automatically

13. Loops: WHILE Loop
DECLARE
TEN number:=10;
i number_table.num%TYPE:=1;
BEGIN
WHILE i <= TEN LOOP
INSERT INTO number_table
VALUES(i);
i := i + 1;
END LOOP;
END;

14. Printing Output
n You need to use a function in the DBMS_OUTPUT
package in order to print to the output
n If you want to see the output on the screen, you
must type the following (before starting):
set serveroutput on format wrapped size 1000000
n Then print using
n dbms_output. put_line(your_string);
n dbms_output.put(your_string);

15. Functions and Procedures
n Up until now, our code was in an anonymous
block
n It was run immediately
n It is useful to put code in a function or
procedure so it can be called several times
n Once we create a procedure or function in a
Database, it will remain until deleted (like a
table).

16. Creating Procedures
CREATE [OR REPLACE] PROCEDURE
procedure_name
[(parameter1 [mode1] datatype1,
parameter2 [mode2] datatype2,
. . .)]
IS|AS
PL/SQL Block;
n Modes:
n IN: procedure must be called with a value for the parameter.
Value cannot be changed
n OUT: procedure must be called with a variable for the
parameter. Changes to the parameter are seen by the user (i.e.,
call by reference)
n IN OUT: value can be sent, and changes to the parameter are
seen by the user
n Default Mode is: IN

17. Example- what does this do?
Table mylog
create or replace procedure
logon_ num_logged
who
num (person IN mylog.who%TYPE,
num OUT mylog.logon_num%TYPE)
IS
Pete 3
BEGIN
select logon_num
into num
John 4 from mylog
where who = person;
END;
Joe 2 /

18. Calling the Procedure
declare
howmany mylog.logon_num%TYPE;
begin
num_logged(‘John',howmany);
dbms_output.put_line(howmany);
end;
/

19. Errors in a Procedure
n When creating the procedure, if there are
errors in its definition, they will not be shown
n To see the errors of a procedure called
myProcedure, type
SHOW ERRORS PROCEDURE myProcedure
in the SQLPLUS prompt
n For functions, type
SHOW ERRORS FUNCTION myFunction

20. Creating a Function
n Almost exactly like creating a
procedure, but you supply a return type
CREATE [OR REPLACE] FUNCTION
function_name
[(parameter1 [mode1] datatype1,
parameter2 [mode2] datatype2,
. . .)]
RETURN datatype
IS|AS
PL/SQL Block;

21. A Function
create or replace function
rating_message(rating IN NUMBER) YOU
NOTE THAT
return VARCHAR2 DON'T SPECIFY THE
AS SIZE
BEGIN
IF rating > 7 THEN
return 'You are great';
ELSIF rating >= 5 THEN
return 'Not bad';
ELSE
return 'Pretty bad';
END IF;
END;
/

22. Calling the function
declare
paulRate:=9;
Begin
dbms_output.put_line(ratingMessage(paulRate));
end;
/

23. Creating a function:
create or replace function squareFunc(num in number)
return number
is
BEGIN
return num*num;
End;
/
Using the function:
BEGIN
dbms_output.put_line(squareFunc(3.5));
END;
/

24. Triggers
n A trigger is a statement that is executed
automatically by the system as a side effect
of a modification to the database.
n To design a trigger mechanism, we must:
n Specify the conditions under which the trigger is
to be executed.
n Specify the actions to be taken when the trigger
executes.

25. Trigger Example
n Suppose that instead of allowing negative
account balances, the bank deals with
overdrafts by
n setting the account balance to zero
n creating a loan in the amount of the overdraft
n giving this loan a loan number identical to the
account number of the overdrawn account
n The condition for executing the trigger is an
update to the account relation that results in
a negative balance value.

26. Trigger Example
create trigger overdraft-trigger after update on account
referencing new row as nrow
for each row
when nrow.balance < 0
begin atomic
insert into borrower
(select customer-name, account-number
from depositor
where nrow.account-number =
depositor.account-number);
insert into loan values
(n.row.account-number, nrow.branch-name,
– nrow.balance);
update account set balance = 0
where account.account-number = nrow.account-number
end