Chapter Seventeen Subprogramming

Chapter SeventeenSubprogramming

Objective:–Procedures

–Functions

–Packages

Chapter 17: Subprogramming 2

Stored Procedures:

• Advantages of Stored Procedures:• Call Stored Procedure from PL/SQL:

Raise_salary ( id, amount);• Call Stored Procedure from SQL:

EXECUTE Raise_salary ( id, amount);

• Running Stored Procedure owned by other user:

EXECUTE Mohsen.Raise_salary ( id, amount);


Stored Procedures:

• Rename Stored Procedure owned by other user:

CREATE SYNONYM my_Raise_salary FOR Mohsen.Raise_salary;

EXECUTE my_Raise_salary ( id, amount);


1 – Procedure Syntax

--Header:

CREATE [OR REPLACE] PROCEDURE P_Name [(P1, P2,..)]

[ IS | AS]

--Local_declarations

--Body:

BEGIN

--Executable_statements

[EXCEPTION exception_handling]

END [P_Name];


Procedures (Example)

PROCEDURE Raise_salary (faculty_ID NUMBER, amount NUMBER) IScurrent_salary NUMBER; -- Declarationsalary_missing EXCEPTION;

BEGINSELECT Salary INTO current_salary --ExecutionFROM FacultyWHERE ID=faculty_ID;IF current_salary IS NULL THEN

RAISE salary_missingELSE

UPDATE FacultySET Salary = Salary + amount WHERE ID= faculty_ID;

END IF; Continued


Procedures (Example)

EXCEPTION --Exception

WHEN NO_DATA_FOUND THEN

INSERT INTO Logfile_Salary

VALUES (Faculty_ID, ‘NOT exist’);

WHEN salary_missing THEN

INSERT INTO Logfile_Salary

VALUES (Faculty_ID, ‘No Salary’);

END Raise_salary;

/


Procedures

-- To call a procedureRaise_Salary(111, 250);

-- To call a procedure without parameters

Proc_one;

Proc_one();


Actual and Formal Parameters:

CREATE PROCEDURE p1 (x: STRING)BEGIN…..END;

--Procedure calln NUMBER(5);p1(n);…SQL> EXEC p1(‘Mary’);


Why Use Subprogramming

a. Extensibility:PROCEDURE NewDept (NewName VARCHAR2, NoFaculty NUMBER) ISBEGIN

INSERT INTO Dept VALUES (NewName, NoFaculty);END;

b. Abstractionc. Modularityd. Reusabilitye. Maintainability


Constrain on Datatypes

CREATE PROCEDURE AddName (Name VARCHAR2(20), …) --illegal

DECLARE

SUBTYPE vchar20 is VARCHAR2(20);

CREATE PROCEDURE AddName (Name vchar20, …)


Procedures (Example 2)

CREATE OR REPLACE PROCEDURE NewStudent (P_first Student.First%TYPE,P_last Student.Last%TYPE,P_Major Student.Major%TYPE)

ASBEGIN

INSERT INTO Student ( ID, First, Last, Major) VALUES (Student_sequence.NEXTVAL, P_first, P_last,

P_Major);END NewStudent;…….NewStudent(‘Jim’, ‘Johnson’, ‘COSC’);


2 – Functions Syntax

[CREATE [OR REPLACE]]

FUNCTION F_Name [(P1, P2,..)] RETURN datatype[ IS | AS]

Local_declarationBEGIN

executable_statements[EXCEPTION exception_handling]END [F_Name];


Functions (Example)

CREATE FUNCTION Salary_OK (Salary REAL, Title VARCHAR2) RETURN BOOLEAN -- HeaderIS

Min_Salary REAL; -- DeclarationMax_Salary REAL;

BEGIN -- ExecutionSELECT L_Sal, H_Sal INTO Min_Salary, Max_SalaryFROM FacultyWHERE Job=Title;RETURN (Salary >= Min_Salary) AND (Salary <= Max_Salary);

END Salary_OK;


Calling Functions

IF Salary_OK(20000,’MANAGER’)

THEN ……….

--

A := Function1();

A := Function1 ;


Calling Functions

DECLAREMyName VARCHAR2(50) := F1();Name VARCHAR2(75) := F2(‘John’);

BEGIN--------

DECLAREa StudentInfo := StudentInfo(111, ‘Mary’, COSC’, 2.4);

BEGIN…

-------DECLARE

FacultyInfo Faculty%ROWTYPE;BEGIN

FacultyInfo := F3(1111);


Parameter Modes

• IN (Default) pass by reference (Read Only)

• OUT pass by value (Write Only)

• IN OUT pass by value (Read & Write)


Example

CREATE PROCEDURE One( a IN INTEGER, c IN OUT INTEGER, b OUT INTEGER) IS

DECLARE x: INTEGER; y: INTEGER ;

Beginb := a; -- legala:= 10; -- illegalb:= 10; -- legalx:= c; -- legaly:=b; --possibly legalc:= 10; -- legal

END;


Comparison of IN, OUT, IN OUT

IN OUT IN OUT Default Pass values to

Formal parameters act like a constant Formal parameter can’t be assigned a value Actual parameter can be constant, initialized variable, literal, or expression

Actual parameter is passed by reference

Must be specified Returns value Formal parameters act like variable Formal parameter must be assigned a value Actual parameter must be a variable

Actual parameter is passed by value; Unless NOCOPY

Must be specified Pass initial value to, returns value Formal parameters act like an initial variable Formal parameter must be assigned a value Actual parameter must be a variable

Actual parameter is passed by value; Unless NOCOPY


Practice:

Create a function to calculate the semester GPA of each student. Call it:

Cal_gpa

-Input student id, semester number.

-Return the GPA for that student.


Positional & Named Subprogram Parameters

PROCEDURE Test (first REAL, second INTEGER) ISBEGIN…..END

--Call procedure TestOne REAL;Two INTEGER;

Test (One, Two); --Positional notationTest (second => Two, first => One); --Named notationTest (first => One, second => Two); --Named notationTest (One, second => Two); --Mixed notation


Concept of NOCOPY

CREATE PROCEDURE Two (S IN OUT

NOCOPY NUMBER , Value OUT NOCOPY num_varray)

BEGIN

…..

END;


Dropping Functions & Procedures• DROP PROCEDURE P_name;

• DROP FUNCTION F_name;


Subprogram Using a Default Value

CREATE PROCEDURE Three (Today DATE DEFAULT SYSDATE,

ZipCode CHAR DEFAULT ‘21532’) IS

BEGIN

….

END;


Default Values

PROCEDURE WhoIs(Name IN VARCHAR2 DEFAULT ‘Hana’,Born_at IN DATE DEFAULT SYSDATE) IS

Begin….. END;--Procedure call

WhoIs (‘Mary’, To_DATE(’01-12-2002’, ‘MM-DD-YYYY));WhoIs(‘Marry’);WhoIs;WhoIs(Born_at => To_DATE(’03-03-1954’, ‘MM-DD-YYYY));


Subprogram within subprogram

PROCEDURE OUTSIDE (date_in IN DATE) ISPROCEDURE inside1 ISBEGIN

…….END;Function inside2 (Next_In IN INTEGER)

RETURN BOOLEANISBEGIN

…..END;

BEGIN -- OUTSIDE….END OUTSIDE;


Recursion

• --n!= n*(n-1)!FUNCTION fact (n POSITIVE) RETURN

INTEGER ISBEGIN

IF n=1 THEN RETURN 1;

ELSERETURN n* fact (n-1);

END IF;END FACT;


Forward Declaration

DECLAREPROCEDURE TWO; --Forward DeclarationPROCEDURE ONE ISBEGIN

TWO;END;PROCDURE TWO ISBEGIN

ONE;END;


Side Effects of Subprogramming Called From SQL

• When a function is called from SELECT, INSERT, UPDATE, or DELETE

the function can not modify any database tables.

• When called from INSERT, UPDATE, or DELETE

the function can not query or modify any database tables modified by that

statement.


Side Effects of Subprogramming Called From SQL

When called from SELECT, INSERT, UPDATE, or DELETE

the function can not execute any:• Control statement

• Session control

• System control statement

• DDL statement


Creating Package Specification:

CREATE [OR REPLACE ] PACKAGE P_name [IS |AS ]

--package specification:

--functions, procedures, variables, --constant, cursors, exceptions

END [P_name];


Packaging subprograms Package Specification:

CREATE PACKAGE Salary_Pack ASSUBTYPE NameType is VARCHAR2(100);

PROCEDURE Hire(Fac_Id INTEGER, Name VARCHAR2);PROCEDURE Fire(Fac_ID INTEGER);PROCEDURE Raise_Salary(Fac_Id INTEGER, Amount REAL);

END Salary_Pack;


Creating Package Body:

Syntax:

CREATE [OR REPLACE] PACKAGE BODY p_name [IS |AS]

--package boady

END p_name;


Packaging subprograms

Package Body:CREATE PACKAGE BODY Salary_Pack AS

PROCEDURE Hire(Fac_Id INTEGER, Name VARCHAR2) ISBEGIN

INSERT INTO faculty VALUES (fac_ID, Name);END;PROCEDURE Fire (Fac_ID INTEGER) ISBEGIN

DELETE FROM Faculty WHERE ID = Fac_ID;END; PROCEDURE Raise_Salary (Fac_Id INTEGER, Amount REAL) ISBegin

UPDATE facultySET Salary = Salary + AmountWHERE ID = Fac_ID;

End;END Salary_Pack;/


Use of Packages

BEGINSalary_Pack.Hire(1111,‘Lorry’)

END;

/


When To Use Packages

• Encapsulation Data (hidden)

• Avoid hard-coding literals

• Grouping together logically related functions


Why Packages

CREATE or REPLACE PROCEDURE fac_name(Fac_ID IN faculty.id%TYPE) IS

FullName VARCHAR2(100);

BEGINSELECT Last_name || ‘, ‘ || first_nameINTO FullNameFROM facultyWHERE faculty.id = Fac_ID;

END;


Why Packages

Problems:1. Length of FullName is hard-coded

2. How about if I want to see ‘first, last’ name?

3. If I need different form of the same code in my applications: How should I maintain my code?


Why Packages

CREATE OR REPLACE PACKAGE faculty_pkg ASSUBTYPE FullName_t IS VARCHAR2(200);

FUNCTION fac_Name (Last_In faculty.last_name%TYPE, First_In faculty.first_name%TYPE)

RETURN fullName_t;

FUNCTION fac_Name(f_id IN faculty.id%TYPE)RETURN fullName_t;

END faculty_pkg;


Why Packages

CREATE OR REPLACE PACKAGE BODY faculty_pkg AS

FUNCTION fac_Name(Last_In faculty.last_name%TYPE, First_In faculty.first_name%TYPE)RETURN fullName_t IS

BEGINRETURN Last_In || ‘, ‘ || First_In

END;


Why Packages

FUNCTION fac_Name(f_id IN faculty.id%TYPE) RETURN fullName_t; IStemp FullName_t;

BEGINSELECT INTO temp fac_name(LastName, FirstName)FROM faculty WHERE faculty.id = id;RETURN temp;

EXCEPTIONWHEN NO_DATA_FOUND THEN

RETURN NULL;WHEN TOO_MANY_ROWS THEN

…..END;

END faculty_pkg;


Package and Local Variables:

CREATE OR REPLACE PACKAGE BODY faculty_pkg IS

TodayDate Date;FUNCTION fac_Name ………..……END fac_Name;……..BEGIN –package

SELECT SYSDATE into TodayDateFROM DUAL;

END faculty_pkg;/


Overloading

CREATE OR REPLACE PACKAGE Student_Pack AS

PROCEDURE AddStudent( P_ID IN Student.id%TYPE,

P_Name IN Student.Name%TYPE,

P_Major IN Student.Major%TYPE);

PROCEDURE AddStudent( P_ID IN Student.id%TYPE,

P_Name IN Student.Name%TYPE);

END Student_Pack;


Overloading

CREATE OR REPLACE PACKAGE BODY Student_Pack ASPROCEDURE AddStudent( P_ID IN Student.id%TYPE,

P_Name IN Student.Name%TYPE,P_Major IN Student.Major%TYPE) IS

BEGININSERT INTO Student(id, Name, Major)VALUES (P_ID, P_Name, P_Major);

END;

PROCEDURE AddStudent( P_ID IN Student.id%TYPE, P_Name IN Student.Name%TYPE) IS

BEGININSERT INTO Student(id, Name)VALUES (P_ID, P_Name);

END;

END Student_Pack;


Restriction on Overloading

• Local or Packaged subprogram, or Type methods can be overloaded

• No overloading of two subprograms with only formal parameter different in name parameter mode or datatype

• No overloading of functions that differ only in return type


Invoker’s Right:

Stored procedure executed with the privilege of their owner; (not current user).

CREATE PROCEDURE addempl(ssn NUMBER, name VARCHAR2,salary NUMBER)

AUTHID CURRENT_USER AS --vs. DEFINER BEGININSERT INTO employee VALUES (ssn, name,

salary);END;_


Invoker’s Right:

USER_USERS:

USERNAME

USER_ID

Default_tablespace

STATUS


Subprogram Location

Subprograms:

• Text

• Compiled: P_code


Subprogram Location

Example

CREATE OR REPLACE PROCEDURE Simple AS

a NUMBER;

BEGIN

a:= 10;

END Simple;


Subprogram Location

• USER_OBJECTS

• USER_SOURCE

• USER_ERRORS

SQL> SELECT OBJECT_NAME, OBJECT_TYPE, STATUS

FROM USER_OBJECTS

WHERE OBJECT_NAME = ‘SIMPLE’;

OBJECT_NAME OBJECT_TYPE STATUS

SIMPLE PROCEDURE VALID


Subprogram Location

SQL> SELECT TEXT

FROM USER_SOURCE

WHERE NAME = ‘SIMPLE’ AND TYPE= ‘PROCEDURE’

ORDER BY line;

TEXT

-----------------------------------------

CREATE OR REPLACE PROCEDURE Simple AS

a NUMBER;

BEGIN

a:= 10;

END Simple;


TABLE FUNCTION

CREATE TYPE Book_Type AS OBJECT(name VARCHAR2(50),author VARCHAR2(30),Description VARCHAR2(500));

CREATE TYPE BookSet_Type AS TABLE of Book_Type;

CREATE TABLE catalogs(Name VARCHAR2(20),cat CLOB);

CREATE FUNCTION GetBooks(a CLOB) RETURN BookSet_Type;

SELECT X.name, y.name, y.other, y.descriptionFROM Catalogs X, TABLE (GetBooks(x.cat)) y;


Find Errors:

• SQL> SHOW ERRORS;-Line number of the error

-Column number of the error

-Text message of the error

• SQL> SELECT line, position, text

FROM USER_ERRORS

WHERE name=‘RAISE_SALARY’ AND TYPE=‘PROCEDURE’;


Explicit Recompilation of Procedures, Functions, Packages

ALTER PROCEDURE name COMPILE;

ALTER FUNCTION name COMPILE;

ALTER PACKAGE name COMPILE;


Why PL/SQL?

CREATE PROCEDURE proc_data (p_input IN VARCHAR2)ASBEGIN

FOR i IN (SELECT *FROM facultyWHERE name LIKE p_input) LOOP

process (i);END LOOP;

END;


Why PL/SQL?

• PL/SQL datatypes are SQL datatypes.

• There is tight coupling between the language and the database.

• No need for OPEN, CLOSE etc.

• Protected from many changes in the database.

• Portable and reusable.

Date post:	02-Jan-2016
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Chapter Seventeen Subprogramming

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