Plsql in oracle

Variable 29• Assigning SQL query results to PL/SQL Variables: ➢ Use SELECT INTO statement... Variable 30• Assigning SQL query results to PL/SQL Variables: ➢ Use SELECT INTO statement...

PL/SQL Statements

in Oracle

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• Introduction to PL/SQL

• Syntax and Data types

• Constants and variable

• PL/SQL statements

• Print messages, raise errors

• Review questions and Exercises

3

Introduction to PL/SQL

4

1.

Introduction to PL/SQL

• Oracle

5

Introduction to PL/SQL

• Oracle Database

6

Introduction to PL/SQL

• Oracle Database

7

Introduction to PL/SQL

• Procedural Language/Structured Query Language).

8

Introduction to PL/SQL

• Procedural Language/Structured Query Language).

• Procedural Language extension of SQL.

9

Introduction to PL/SQL

• Procedural Language/Structured Query Language).

• Procedural Language extension of SQL.

• Environment: Oracle Database

10

Introduction to PL/SQL

• PL/SQL Developer:

11

Syntax and Data types

12

2.

Syntax and Data types

Syntax and Data types

• Syntax of block:

14

Syntax and Data types

• Symbols:

15

Syntax and Data types

Syntax and Data types

Syntax and Data types

Syntax and Data types

Syntax and Data types

Syntax and Data types

• Scalar:

➢ Datetime:

▪ Example: “01-OCT-12” – “DD-MON-YY”

21

Syntax and Data types

Syntax and Data types

• User-defined:

23

Constants and variable

24

3.

Variable 25

• Variable declaration:

➢ specific data type

➢ variable names are not case-sensitive, not

exceed 30 characters

➢ cannot use a reserved PL/SQL keyword

Variable 27

• Initializing Variables:

➢ The DEFAULT keyword

greetings varchar2(20) DEFAULT 'Have a Good Day';

➢ The assignment operator

counter binary_integer := 0;

Variable 28

• Variables Scope:

➢ Local variables

➢ Global variables

Variable 29

• Assigning SQL query results to PL/SQL Variables:

➢ Use SELECT INTO statement

Variable 30

• Assigning SQL query results to PL/SQL Variables:

➢ Use SELECT INTO statement

Constant 31

• Declaring a constant:

Ex:

PI CONSTANT NUMBER := 3.141592654;

PL/SQL statements

32

4.

PL/SQL Statements 33

IF – THEN 35

IF condition THEN

S;

END IF;

Condition: a Boolean or relational condition

S: a simple or compound statement

IF – THEN 36

IF (a <= 20) THEN

c:= c+1;

END IF;

Condition: a Boolean or relational condition

S1, S2: a simple or compound statement

IF – THEN – ELSE 38

IF color = red THEN

dbms_output.put_line(‘Oh yeah RED')

ELSE

dbms_output.put_line(‘Why not RED');

END IF;

IF – THEN – ELSIF 39

IF(boolean_expression 1)THEN

S1; Executes when the boolean expression 1 is true

ELSIF( boolean_expression 2) THEN

S2; Executes when the boolean expression 2 is true

ELSIF( boolean_expression 3) THEN

S3; Executes when the boolean expression 3 is true

ELSE

S4; executes when the none of the above condition is true END IF;

CASE Statement 41

CASE selector

WHEN 'value1' THEN S1;

WHEN 'value2' THEN S2;

WHEN 'value3' THEN S3;

ELSE Sn; default case

END CASE;

CASE Statement 42

CASE grade

when 'A' then dbms_output.put_line('Excellent');

when 'B' then dbms_output.put_line('Very good');

when 'C' then dbms_output.put_line('Well done');

when 'D' then dbms_output.put_line('You passed');

when 'F' then dbms_output.put_line('Better try again'); else dbms_output.put_line('No such grade');

END CASE;

Searched CASE Statement 43

CASE

WHEN selector = 'value1' THEN S1;

WHEN selector = 'value2' THEN S2;

WHEN selector = 'value3' THEN S3;

ELSE Sn; default case

END CASE;

Searched CASE Statement 44

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('Well done');

when grade = 'D' then dbms_output.put_line('You passed');

when grade = 'F' then dbms_output.put_line('Better try again'); else dbms_output.put_line('No such grade');

end case;

• Loop control statements:

• Exit (and exit when)

• Continue

• Goto

PL/SQL Basic Loop 46

LOOP

Sequence of statements;

END LOOP;

PL/SQL While loop 49

WHILE condition LOOP

sequence_of_statements

END LOOP;

PL/SQL For loop 52

FOR a in 10 20 LOOP

dbms_output.put_line('value of a: ' || a);

END LOOP;

Loops may be nested also 53

WHILE condition1 LOOP

Cursor 54

• A cursor is a pointer to a context area.

• A cursor holds the rows (one or more) returned by a SQL statement.

• The set of rows the cursor holds is referred to as the

active set.

• There are implicit cursors and explicit cursors

Implicit and explicit cursor 55

• Implicit cursor is automatically created whenever an

SQL statement is executed (INSERT, UPDATE, and

DELETE), when there is no explicit cursor for the

statement Any SQL cursor attribute will be accessed as sql%attribute_name

• Explicit cursors are programmer-defined cursors for

gaining more control over the context area It is created

on a SELECT Statement which returns more than one

row.

Opening the Cursor 58

Opening the cursor allocates the memory for the

cursor and makes it ready for fetching the rows

returned by the SQL statement into it

OPEN c_customers;

Fetching the Cursor 59

Fetching the cursor involves accessing one row at a

time

FETCH c_customers INTO c_id, c_name, c_addr;

Closing the Cursor 60

Closing the cursor means releasing the allocated

memory

CLOSE c_customers;

Cursor using example 61

Cursor using example 62

BEGIN

OPEN c_customers;

LOOP

FETCH c_customers into c_id, c_name, c_addr;

EXIT WHEN c_customers%notfound;

dbms_output.put_line(c_id || ' ' || c_name || ' ' || c_addr); END LOOP;

CLOSE c_customers;

END;

Print messages, raise errors

63

5.

Print messages, raise errors

• Print message:

➢ Syntax:

DBMS_OUTPUT.PUT_LINE(‘messages’)

64

Print messages, raise errors

• Print message:

➢ Example:

65

Print messages, raise errors

• Exception:

➢ Syntax:

66

Print messages, raise errors

• Exception:

67

Print messages, raise errors

• Two types of exception:

➢ System-defined exceptions

➢ User-defined exceptions

68

Print messages, raise errors

Print messages, raise errors

• User-defined exception:

➢ Syntax:

70

Print messages, raise errors

• Raising Exceptions:

➢ Syntax:

71

Print messages, raise errors

• Example:

72

Review questions and Exercises

73

6.

Exercises

• Write a PL/SQL block to differenciate between

CHAR and VARCHAR2 datatype

Exercises

Exercises

• Write a PL/SQL block display the discription

against a grade using CASE statement

Exercises

Exercises

Exercises

• Write a PL/SQL block to print numbers from 0 to 9 using LOOP and FOR LOOP

Exercises

LOOP

Exercises

LOOP

Exercises

FOR LOOP

Exercises

FOR LOOP

Exercises

• Write a PL/SQL block to check whether a number

is positive, negative or zero

Exercises

Exercises

Exercises

• Write a PL/SQL block to check whether a number

is prime or not

Exercises

Exercises