Oracle collection ( Index-by table || Nested table || V array)

STUDENT BLOG

In a collection, the internal components always have the same data type, and are called elements. You can access each element of a collection variable by its unique index, with this syntax: variable_name(index). To create a collection variable, you either define a collection type and then create a variable of that type or use %TYPE.

In a record, the internal components can have different data types, and are called fields. You can access each field of a record variable by its name, with this syntax: variable_name.field_name. To create a record variable, you either define a RECORD type and then create a variable of that type or use %ROWTYPE or %TYPE.

Collection Types

1)Index-by table

2)Nested table

3)V array

4)PL/SQL Record

5)Ref cursors

1)Index-by table  

syntax:-

TYPE type_name IS TABLE OF element_type [NOT NULL] INDEX BY subscript_type; 
 
table_name type_name;

Example

Following example shows how to create a table to store integer values along with names and later it prints the same list of names.

DECLARE 
   TYPE salary IS TABLE OF NUMBER INDEX BY VARCHAR2(20); 
   salary_list salary; 
   name   VARCHAR2(20); 
BEGIN 
   -- adding elements to the table 
   salary_list('Rajnish') := 62000; 
   salary_list('Minakshi') := 75000; 
   salary_list('Martin') := 100000; 
   salary_list('James') := 78000;  
   
   -- printing the table 
   name := salary_list.FIRST; 
   WHILE name IS NOT null LOOP 
      dbms_output.put_line 
      ('Salary of ' || name || ' is ' || TO_CHAR(salary_list(name))); 
      name := salary_list.NEXT(name); 
   END LOOP; 
END; 
/

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

Salary of James is 78000 
Salary of Martin is 100000 
Salary of Minakshi is 75000 
Salary of Rajnish is 62000  

PL/SQL procedure successfully completed.

Example

Elements of an index-by table could also be a %ROWTYPE of any database table or %TYPE of any database table field. The following example illustrates the concept. We will use the CUSTOMERS table stored in our database as −

Select * from customers;  

+----+----------+-----+-----------+----------+ 
| ID | NAME     | AGE | ADDRESS   | SALARY   | 
+----+----------+-----+-----------+----------+ 
|  1 | Ramesh   |  32 | Ahmedabad |  2000.00 | 
|  2 | Khilan   |  25 | Delhi     |  1500.00 | 
|  3 | kaushik  |  23 | Kota      |  2000.00 | 
|  4 | Chaitali |  25 | Mumbai    |  6500.00 | 
|  5 | Hardik   |  27 | Bhopal    |  8500.00 | 
|  6 | Komal    |  22 | MP        |  4500.00 | 
+----+----------+-----+-----------+----------+  

DECLARE 
   CURSOR c_customers is 
      select name from customers; 

   TYPE c_list IS TABLE of customers.Name%type INDEX BY binary_integer; 
   name_list c_list; 
   counter integer :=0; 
BEGIN 
   FOR n IN c_customers LOOP 
      counter := counter +1; 
      name_list(counter) := n.name; 
      dbms_output.put_line('Customer('||counter||'):'||name_lis t(counter)); 
   END LOOP; 
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  

PL/SQL procedure successfully completed

2)Nested table

syntax:-

TYPE type_name IS TABLE OF element_type [NOT NULL]; 
table_name type_name; 

This declaration is similar to the declaration of an index-by table, but there is no INDEX BY clause.

Example:-

DECLARE 
   TYPE names_table IS TABLE OF VARCHAR2(10); 
   TYPE grades IS TABLE OF INTEGER;  
   names names_table; 
   marks grades; 
   total integer; 
BEGIN 
   names := names_table('Kavita', 'Pritam', 'Ayan', 'Rishav', 'Aziz'); 
   marks:= grades(98, 97, 78, 87, 92); 
   total := names.count; 
   dbms_output.put_line('Total '|| total || ' Students'); 
   FOR i IN 1 .. total LOOP 
      dbms_output.put_line('Student:'||names(i)||', Marks:' || marks(i)); 
   end loop; 
END; 
/  

out put:-

Total 5 Students 
Student:Kavita, Marks:98 
Student:Pritam, Marks:97 
Student:Ayan, Marks:78 
Student:Rishav, Marks:87 
Student:Aziz, Marks:92  

PL/SQL procedure successfully completed. 

3)V Array

CREATE OR REPLACE TYPE varray_type_name IS VARRAY(n) of <element_type>

Example 

DECLARE 
   type namesarray IS VARRAY(5) OF VARCHAR2(10); 
   type grades IS VARRAY(5) OF INTEGER; 
   names namesarray; 
   marks grades; 
   total integer; 
BEGIN 
   names := namesarray('Kavita', 'Pritam', 'Ayan', 'Rishav', 'Aziz'); 
   marks:= grades(98, 97, 78, 87, 92); 
   total := names.count; 
   dbms_output.put_line('Total '|| total || ' Students'); 
   FOR i in 1 .. total LOOP 
      dbms_output.put_line('Student: ' || names(i) || ' 
      Marks: ' || marks(i)); 
   END LOOP; 
END; 
/

output:-

Total 5 Students 
Student: Kavita  Marks: 98 
Student: Pritam  Marks: 97 
Student: Ayan  Marks: 78 
Student: Rishav  Marks: 87 
Student: Aziz  Marks: 92 

PL/SQL procedure successfully completed.