Plsql

What is PL/SQL
– Procedural Language – SQL
– An extension to SQL with design features of programming
languages (procedural and object oriented)
– PL/SQL and Java are both supported as internal host
languages within Oracle products.

Why PL/SQL
– Acts as host language for stored procedures and triggers.
– Provides the ability to add middle tier business logic to client/server
applications.
– Provides Portability of code from one environment to another
– Improves performance of multi-query transactions.
– Provides error handling

PL/SQL BLOCK
STRUCTURE
DECLARE (optional)
- variable declarations
BEGIN (required)
- SQL statements
- PL/SQL statements or sub-blocks
EXCEPTION (optional)
- actions to perform when errors occur
END; (required)

PL/SQL Block Types
Anonymous
DECLARE
BEGIN
-statements
EXCEPTION
END;
Procedure
PROCEDURE <name>
IS
BEGIN
-statements
EXCEPTION
END;
Function
FUNCTION <name>
RETURN <datatype>
IS
BEGIN
-statements
EXCEPTION
END;

PL/SQL Variable Types
• Scalar (char, varchar2, number, date, etc)
• Composite (%rowtype)
• Reference (pointers)
• LOB (large objects)
Note: Non PL/SQL variables include bind variables,
host (“global”) variables, and parameters.

Variable Naming
Conventions
– Two variables can have the same name if they are in
different blocks (bad idea)
– The variable name should not be the same as any table
column names used in the block.

PL/SQL is strongly typed
– All variables must be declared before their use.
– The assignment statement
: =
is not the same as the equality operator
=
– All statements end with a ;

PL/SQL Sample Program
Variable g_inv_value number
DECLARE
v_price number(8,2) := 10.25;
v_quantity number(8,0) := 400;
BEGIN
:g_inv_value := v_price * v_quantity;
END;
/
Print g_inv_value
/

Set serveroutput on
DECLARE
v_inv_value number(10,2);
v_price number(8,2) := 10.25;
BEGIN
v_inv_value := v_price * v_quantity;
dbms_output.put('The value is: ');
dbms_output.put_line(v_inv_value);
END;
/

(with user input)
Set serveroutput on
Accept p_price Prompt 'Enter the Price: '
DECLARE
v_inv_value number(8,2);
v_price number(8,2);
BEGIN
v_price := &p_price;
v_inv_value := v_price * v_quantity;
dbms_output.put_line('******');
dbms_output.put_line('price * quantity=');
dbms_output.put_line(v_inv_value);
END;
/ Note: PL/SQL not designed for user interface programming

PL/SQL Comments
DECLARE
v_salary number(9,2) := 40000;
BEGIN
/* this is a multi-line comment that
will be ignored by the pl/sql
interpreter */
v_salary := v_salary * 2; -- nice raise
END; -- end of program

SELECT INTO
SET SERVEROUTPUT ON
DECLARE
v_max_gpa number(3,2);
v_numstudents number(4);
v_lname students.lname%type;
v_major students.major%type;
BEGIN
select max(gpa) into v_max_gpa
from students;
DBMS_OUTPUT.PUT_LINE ('The highest GPA is '||v_max_gpa);
select count(sid) into v_numstudents
from students
where gpa = v_max_gpa;
IF v_numstudents > 1 then
DBMS_OUTPUT.PUT_LINE ('There are '||v_numstudents||' with that GPA');
ELSE
select lname, major into v_lname, v_major
from students
where gpa=v_max_gpa;
DBMS_OUTPUT.PUT_LINE ('The student name is '||v_lname);
DBMS_OUTPUT.PUT_LINE ('The student major is '||v_major);
END IF;
END;
/

Cont…..
If the SELECT statement identifies more than one row to be
fetched ,Oracle Database will raise the TOO_MANY_ROWS exception.
If the statement doesn’t identify any rows to be fetched, Oracle
Database will raise the NO_DATA_FOUND exception.
Here are some examples of using SELECT-INTO:
Get the last name for a specific employee ID (the primary key in the
employees table):
DECLARE l_last_name employees.last_name%TYPE; BEGIN SELECT
last_name INTO l_last_name FROM employees WHERE employee_id =
138; DBMS_OUTPUT.put_line ( l_last_name); END;

Fetch columns from different tables
– Fetch columns from different tables:
– DECLARE l_last_name employees.last_name%TYPE;
l_department_name departments.department_name%TYPE; BEGIN
SELECT last_name, department_name INTO l_last_name,
l_department_name FROM employees e, departments d WHERE
e.department_id=d.department_id AND e.employee_id=138;
DBMS_OUTPUT.put_line ( l_last_name || ' in ' ||
l_department_name); END;

%ROWTYPE
Set serveroutput on
DECLARE
v_student students%rowtype;
BEGIN
select * into v_student
from students
where sid='123456';
DBMS_OUTPUT.PUT_LINE (v_student.lname);
DBMS_OUTPUT.PUT_LINE (v_student.major);
DBMS_OUTPUT.PUT_LINE (v_student.gpa);
END;
/

CURSORS
– A cursor is a private set of records
– An Oracle Cursor = VB recordset = JDBC ResultSet
– Implicit cursors are created for every query made in Oracle
(predefine)
– Explicit cursors can be declared by a programmer within
PL/SQL. {jo programmer banata ha}

Cursor Attributes
– cursorname%ROWCOUNT Rows returned so far
– cursorname%FOUND One or more rows retrieved
– cursorname%NOTFOUND No rows found
– Cursorname%ISOPEN Is the cursor open

Explicit Cursor Control
– Declare the cursor
– Open the cursor
– Fetch a row
– Test for end of cursor
– Close the cursor
Note: there is a FOR LOOP available with an implicit fetch

Cursor declaration
– 1) Declaring a Cursor in the Declaration Section:
– DECLARE CURSOR emp_cur IS SELECT * FROM emp_tbl
WHERE salary > 5000;

How to access an Explicit
Cursor?
• These are the three steps in accessing the cursor.
1) Open the cursor.
2) Fetch the records in the cursor one at a time.
3) Close the cursor.
• General Syntax to open a cursor is:
• OPEN cursor_name; General Syntax to fetch records from a
cursor is:
• FETCH cursor_name INTO record_name; OR
FETCH cursor_name INTO variable_list; General Syntax to
close a cursor is:
• CLOSE cursor_name;

Using Loops with Explicit
Cursors:
• Cursor with a Simple Loop:
• 1> DECLARE
• 2> CURSOR emp_cur IS
• 3> SELECT first_name, last_name, salary FROM emp_tbl;
• 4> emp_rec emp_cur%rowtype;
• 5> BEGIN
• 6> IF NOT sales_cur%ISOPEN THEN
• 7> OPEN sales_cur;
• 8> END IF;
• 9> LOOP
• 10> FETCH emp_cur INTO emp_rec;
• 11> EXIT WHEN emp_cur%NOTFOUND;
• 12> dbms_output.put_line(emp_cur.first_name || ' ' ||emp_cur.last_name
• 13> || ' ' ||emp_cur.salary);
• 14> END LOOP;
• 15> END;
• 16> /

Cursor with a While
Loop:
• Lets modify the above program to use while loop.
• 1> DECLARE
• 5> BEGIN
• 6> IF NOT sales_cur%ISOPEN THEN
• 7> OPEN sales_cur;
• 8> END IF;
• 9> FETCH sales_cur INTO sales_rec;
• 10> WHILE sales_cur%FOUND THEN
• 11> LOOP
• 12> dbms_output.put_line(emp_cur.first_name || ' ' ||emp_cur.last_name
• 13> || ' ' ||emp_cur.salary);
• 14> FETCH sales_cur INTO sales_rec;
• 15> END LOOP;
• 16> END;

Cursor with a FOR Loop:
• When using FOR LOOP you need not declare a record
or variables to store the cursor values, need not open,
fetch and close the cursor. These functions are
accomplished by the FOR LOOP automatically.
• General Syntax for using FOR LOOP:
• FOR record_name IN cusror_name
• LOOP
• process the row...
• END LOOP;

• Let’s use the above example to learn how to use for loops in cursors.
• 1> DECLARE
• 5> BEGIN
• 6> FOR emp_rec in sales_cur
• 7> LOOP
• 8> dbms_output.put_line(emp_cur.first_name || ' ' ||emp_cur.last_name 9> || ' ' ||emp_cur.salary);
• 10> END LOOP;
• 11>END;
• 12> /

Sample Cursor Program
DECLARE
CURSOR students_cursor IS
SELECT * from students;
v_student students_cursor%rowtype;
/* instead we could do v_student students%rowtype */
BEGIN
DBMS_OUTPUT.PUT_LINE ('******************');
OPEN students_cursor;
FETCH students_cursor into v_student;
WHILE students_cursor%found LOOP
DBMS_OUTPUT.PUT_LINE (v_student.last);
DBMS_OUTPUT.PUT_LINE (v_student.major);
FETCH students_cursor into v_student;
END LOOP;
CLOSE students_cursor;
END;
/

Sample Cursor Program
(same program without composite variable)
DECLARE
CURSOR students_cursor IS
SELECT last, major from students;
v_Last students.last%type;
v_major students.major%type;
BEGIN
OPEN students_cursor;
FETCH students_cursor into v_last, v_major;
WHILE students_cursor%found LOOP
DBMS_OUTPUT.PUT_LINE (v_last);
DBMS_OUTPUT.PUT_LINE (v_major);
FETCH students_cursor into v_last, v_major;
END LOOP;
CLOSE students_cursor;
END;
/

When is PL/SQL handy
• When something is too complicated for SQL
• When conditional branching and looping are needed
• Example
• Write a PL/SQL program that assigns email address to each employee or student in
a table. Following these rules:
- email address should be all lower case
- email address should default to first initial plus the first seven letters of the last name
- email can be no longer than eight characters
- if email is already used than use first initial plus middle initial plus first
six letters of last name
- if the previous address is taken use the first two letters of the first name
and the first six letters of the last name.
- if the previous address is taken use first six letters of last name + 01 or 02 …etc

Function
– PL/SQL user defined function stored in the database and executed when a
function call is made in code: example x := SQUARED(50)
– Example:
Create or Replace Function SQUARED
(p_number_to_square IN number)
RETURN number
IS
v_answer number(10);
BEGIN
v_answer := p_number_to_square * p_number_to_square;
RETURN(v_answer);
END;
/

Plsql

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Plsql