PL/SQL - Packages

PL/SQL - Packages

In this chapter, we will discuss the Packages in PL/SQL. Packages are schema objects that groups logically related PL/SQL types, variables, and subprograms.
A package will have two mandatory parts −

1.Package specification
2.Package body or definition

Package Specification

The specification is the interface to the package. It just DECLARES the types, variables, constants, exceptions, cursors, and subprograms that can be referenced from outside the package. In other words, it contains all information about the content of the package, but excludes the code for the subprograms.
All objects placed in the specification are called public objects. Any subprogram not in the package specification but coded in the package body is called a private object.
The following code snippet shows a package specification having a single procedure. You can have many global variables defined and multiple procedures or functions inside a package.

CREATE PACKAGE cust_sal AS 
   PROCEDURE find_sal(c_id customers.id%type); 
END cust_sal; 
/

When the above code is executed at the SQL prompt, it produces the following result −
Package created.

Package Body

The package body has the codes for various methods declared in the package specification and other private declarations, which are hidden from the code outside the package.
The CREATE PACKAGE BODY Statement is used for creating the package body. The following code snippet shows the package body declaration for the cust_sal package created above. I assumed that we already have CUSTOMERS table created in our database as mentioned in the PL/SQL - Variables chapter.

CREATE OR REPLACE PACKAGE BODY cust_sal AS  
   
   PROCEDURE find_sal(c_id customers.id%TYPE) IS 
   c_sal customers.salary%TYPE; 
   BEGIN 
      SELECT salary INTO c_sal 
      FROM customers 
      WHERE id = c_id; 
      dbms_output.put_line('Salary: '|| c_sal); 
   END find_sal; 
END cust_sal; 
/

When the above code is executed at the SQL prompt, it produces the following result −
Package body created.

Using the Package Elements

The package elements (variables, procedures or functions) are accessed with the following syntax −

package_name.element_name;

Consider, we already have created the above package in our database schema, the following program uses the find_sal method of the cust_sal package −

DECLARE 
   code customers.id%type := 1; 
BEGIN 
   cust_sal.find_sal(code); 
END; 
/

When the above code is executed at the SQL prompt, it prompts to enter the customer ID and when you enter an ID, it displays the corresponding salary as follows −
Enter value for cc_id: 1
Salary: 3000

PL/SQL procedure successfully completed.
Example
The following program provides a more complete package. We will use the CUSTOMERS table stored in our database with the following records −

Select * from customers;  

+----+----------+-----+-----------+----------+ 
| ID | NAME     | AGE | ADDRESS   | SALARY   | 
+----+----------+-----+-----------+----------+ 
|  1 | Ramesh   |  32 | Ahmedabad |  3000.00 | 
|  2 | Khilan   |  25 | Delhi     |  3000.00 | 
|  3 | kaushik  |  23 | Kota      |  3000.00 | 
|  4 | Chaitali |  25 | Mumbai    |  7500.00 | 
|  5 | Hardik   |  27 | Bhopal    |  9500.00 | 
|  6 | Komal    |  22 | MP        |  5500.00 | 
+----+----------+-----+-----------+----------+

The Package Specification

CREATE OR REPLACE PACKAGE c_package AS 
   -- Adds a customer 
   PROCEDURE addCustomer(c_id   customers.id%type, 
   c_name customers.Name%type, 
   c_age  customers.age%type, 
   c_addr customers.address%type,  
   c_sal  customers.salary%type); 
   
   -- Removes a customer 
   PROCEDURE delCustomer(c_id  customers.id%TYPE); 
   --Lists all customers 
   PROCEDURE listCustomer; 
  
END c_package; 
/

When the above code is executed at the SQL prompt, it creates the above package and displays the following result −
Package created.

Creating the Package Body
CREATE OR REPLACE PACKAGE BODY c_package AS 

   PROCEDURE addCustomer(c_id  customers.id%type, 
      c_name customers.Name%type, 
      c_age  customers.age%type, 
      c_addr  customers.address%type,  
      c_sal   customers.salary%type) 
   IS 
   BEGIN 
      INSERT INTO customers (id,name,age,address,salary) 
         VALUES(c_id, c_name, c_age, c_addr, c_sal); 
   END addCustomer; 
   
   PROCEDURE delCustomer(c_id   customers.id%type) IS 
   BEGIN 
      DELETE FROM customers 
      WHERE id = c_id; 
   END delCustomer; 
   
   
   PROCEDURE listCustomer IS 
   CURSOR c_customers is 
      SELECT  name FROM customers; 
   TYPE c_list is TABLE OF customers.Name%type; 
   name_list c_list := c_list(); 
   counter integer :=0; 
   BEGIN 
      FOR n IN c_customers LOOP 
      counter := counter +1; 
      name_list.extend; 
      name_list(counter) := n.name; 
      dbms_output.put_line('Customer(' ||counter|| ')'||name_list(counter)); 
      END LOOP; 
   END listCustomer;
   
END c_package; 
/

The above example makes use of the nested table. We will discuss the concept of nested table in the next chapter.
When the above code is executed at the SQL prompt, it produces the following result −
Package body created.

Using The Package

The following program uses the methods declared and defined in the package c_package.

DECLARE 
   code customers.id%type:= 8; 
BEGIN 
   c_package.addcustomer(7, 'Rajnish', 25, 'Chennai', 3500); 
   c_package.addcustomer(8, 'Subham', 32, 'Delhi', 7500); 
   c_package.listcustomer; 
   c_package.delcustomer(code); 
   c_package.listcustomer; 
END; 
/ 

When the above code is executed at the SQL prompt, it produces the following result −

Customer(1): Ramesh
Customer(2): Khilan
Customer(3): kaushik
Customer(4): Chaitali
Customer(5): Hardik
Customer(6): Komal
Customer(7): Rajnish
Customer(8): Subham
Customer(1): Ramesh
Customer(2): Khilan
Customer(3): kaushik
Customer(4): Chaitali
Customer(5): Hardik
Customer(6): Komal
Customer(7): Rajnish

PL/SQL procedure successfully completed