Pl/SQL, cursors, records

1. PL/SQL

2. What is PL/SQL?
• PL/SQL is a block-structured language.
• A block lets you group logically related
declarations and statements.

3. What is PL/SQL?
• A PL/SQL block has three parts:
– Optional DECLARATIVE part,
– an executable part, and
– Optional EXCEPTION-HANDLING part.
[Block header]
[DECLARE <constants> <variables> <cursors>]
[BEGIN]
<PL/SQL statements>
[EXCEPTION exception handling routine>]
END;

4. Types of Block
• Anonymous Block
– Are blocks without header
• Named Block
– Blocks having headers
– Can be either Subprogram or triggers
– Can be compiled separately and stored
permanently in an Oracle database, Ready to be
executed

5. Variables and Constant
• Must declare a constant or
variable before referencing it in other
statements in a declarative part of the block
• Declaring Variable
variablename datatype[(size)] [:= initial value]

6. Variables and Constant
• Variable Declaration
– Bound Declaration
• Specify size for a variable
• Example: age NUMBER(2); --store 2 digits
– Unbound Declaration
• Allocate maximum memory allowed for that particular
type
• Example: age NUMBER;

7. Variables and Constant
• Variable Declaration
– Anchored Declaration
• Variable is declared with another variable or a
table column
• %TYPE is used for anchor declaration.
variablename object%TYPE[:= initial value]
• Example: num1 NUMBER[5];
num2 num%TYPE;
empsal EMPLOYEE.SALARY%TYPE;

8. Variable and Constant
• Assigning Values to a Variable
– Assignment operator := is used to assign value to a
variable.
variablename:=<value/expression>
• Commenting Your Code
– Single Line Comment: starts with double ‘-’
– Multiple Line Comment: /*...*/

9. Variables and Constants
• Literal
– It is a simply a value, which is not represented by an
identifier
• Constant
– Named literal is called constant
– Declaring Constant
constant_name CONSTANT datatype[(size)] := initial value]
Example: pi CONSTANT NUMBER:=3.14;

10. PL/SQL DATATYPES

11. PL/SQL Datatypes
• Datatype identify type of data and associated
operation for handling it.
• PL/SQL provides
– Scalar types
– Composite types
– Reference types
– LOB types

12. 1.Scalar Types
• It is atomic.
– Not made up of other dataypes.
• It holds a single value, such as a number or
character string.
• Falls into four types
– PL/SQL Number Types
– PL/SQL Character and String Types
– PL/SQL Boolean Types
– PL/SQL Date, Time, and Interval Types

13. 1.Scalar Types
• PL/SQL Number Types
– BINARY_DOUBLE, BINARY_FLOAT, BINARY_INTEGER,
DEC, DECIMAL, DOUBLE PRECISION, FLOAT, INT,
INTEGER, NATURAL, NATURALN, NUMBER, NUMERIC,
PLS_INTEGER, POSITIVE, POSITIVEN, REAL, SIGNTYPE,
SMALLINT
• PL/SQL Character and String Types
– CHAR, CHARACTER, LONG, LONG RAW, NCHAR,
NVARCHAR2, RAW, ROWID, STRING, UROWID,
VARCHAR, VARCHAR2

14. 1.Scalar Types
• PL/SQL Boolean Types
– BOOLEAN
• PL/SQL Date, Time, and Interval Types
– DATE, TIMESTAMP, TIMESTAMP WITH TIMEZONE,
TIMESTAMP WITH LOCAL TIMEZONE, INTERVAL
YEAR TO MONTH, INTERVAL DAY TOSECOND

15. 2. Composite Type
• Made up with other datatypes such as the
elements of an ARRAY, RECORD, or TABLE.

16. 3. Reference Datatypes
• A reference type holds values, called pointers,
that designate other program items.
• Include REF CURSORS and REFs to object
types.

17. 4. LOB Types
• A LOB type holds values, that specify the
location of large objects, such as text blocks or
graphic images, that are stored separately
from other database data.
• LOB types include BFILE, BLOB, CLOB,
and NCLOB

18. Printing in PL/SQL
• Procedures of DBMS_OUTPUT package is used
– DBMS_OUTPUT.PUT(string)
– DBMS_OUTPUT.PUT_LINE(string)
• Before using this package run the command
– SET SERVEROUTPUT ON

19. Writing and Executing PL/SQL Program
• Writing
– Write code in Notepad.
– SQL code files have extension .sql
• Executing
– Give following commands
• @ completefilename -OR-
• EXEC completefilename
Example: @d:mycodeaddition
-in the following line type / to execute

20. PL/SQL CONTROL STRUCTURE

21. 1. Conditional Control Statement IF
Syntax 1:
IF condition
THEN
.....
END IF;
Syntax 2:
IF condition
THEN
.....
ELSE
.....
END IF;

22. 1. Conditional Control Statement IF
Syntax 3:
IF condition
THEN
.....
ELSIF condition
THEN
.....
ELSIF condition
THEN
.....
ELSE
.....
END IF;

23. 2. CASE Statement
• The CASE statement selects one sequence of
statements to execute.
CASE selector
WHEN value THEN ....
WHEN value THEN...
.....
ELSE .....
END CASE;

24. 3. Using LOOP statement
LOOP
statement(s);
END LOOP;
• Force simple to stop using statements
EXIT;
EXIT WHEN <condition>;

25. 4. While Loop
• The WHILE-LOOP statement executes the
statements in the loop body as long as a
condition is true.
WHILE condition
LOOP
sequence_of_statements
END LOOP;

26. 5. FOR Loop
• FOR loops iterate over a specified range of
integers.
• A double dot (..) serves as the range operator
FOR loopvariable IN [REVERSE} lowest..highest
LOOP
<statement(s);
END LOOP;

27. DATABASE INTERACTION IN PL/SQL

28. • You can use following SQL statement in
PL/SQL code
– SELECT
– INSERT
– DELETE
– UPDATE

29. SELECT INTO statement
• SELECT INTO statement is used to store the
result in variable where PL/SQL access it and
manipulate it.
SELECT column_list INTO variable_list
FROM tablename
[WHERE condition]
Example: SELECT empno,salary INTO eno, sal
FROM employee WHERE empno=5;

33. SELECT INTO statement
• Where would you store data?????
SELECT * INTO ????????
FROM ....
....
• Solution
– Declare variable for each column
– USE records

34. USING RECORDS

35. Using RECORDS
• A record is a group of multiple piece of
information, related to one another called
fields.
• Types of Records
– Table Based Records
– Programmer Defined Records
– Cursor Based Records

36. Table Based Records
• Represents each fields of a table
• %ROWTYPE is used to declared table based
record.
record_name table_name%ROWTYPE;
• Example
emp_rec employee%ROWTYPE;

37. Table Based Records
• Accessing individual fields using dot(.)
record_name.field_name
Example:
SELECT * INTO emp_rec
FROM employee
WHERE empno=5
dbms_output.put_line(emp_rec.Name);

38. Programmer Based Record
• TYPE statement is used to defined
programmer defined record.
• Firstly RECORD type is defined with TYPE
statement then declare variable of RECORD
type.
TYPE <typename> IS RECORD
(fields declaration);

39. Programmer Based Record
• Example
declare
type empType IS RECORD
(eno number, ename varchar(20));
emp_rec empType;
begin
SELECT empno,name INTO emp_rec
....
end;

40. NOTE
• IF a SELECT INTO statement return more than
one rows, Oracle return ERROR message.
• Solution
– CURSOR

41. CURSORS IN PL/SQL

42. PL/SQL Cursor
• Cursor is a mechanism that provides a way to
select multiple rows of data from a table and
then process each row individually inside
PL/SQL block.
• Set of rows returned by multi row query is
called Result Set or Active Set.
– Context Area contain result set.
– Cursor is pointer to this context Area.

43. Types of Cursor
• Implicit Cursor
– Declared for all DML and SELECT that return one
row
• Explicit Cursor
– Used for queries that return more than one data.
– Declared and named by programmer.

44. Explicit Cursor
• Four Steps
1. Declare Cursor
• Declared in declaration part
CURSOR cursorname IS select statement
2. Open Cursor
• Activates query and identification of rows satisfy
query
OPEN cursorname;

45. Explicit Cursor
• Four Steps
3. Fetch Rows
• Retrieves rows individually
FETCH cursorname INTO record_list
4. Close Cursor
• Close the cursor and release the resources
CLOSE cursorname;

46. Explicit Cursor Attributes
• %NOTFOUND attribute
• %FOUND attribute
• %ROWCOUNT attribute
• %ISOPEN attribute

47. ADVANTAGES OF PL/SQL

48. • Support for SQL
• Better Performance
• Higher Productivity
• Full Portable
• Tight Integration with SQL
• Security