PL/SQL COLLECTION

In PL/SQL, you can create collections to store multiple values of the same datatype.

There are three main types of collections in PL/SQL: associative arrays (also known as index-by tables), nested tables, and VARRAYs (variable-size arrays).

 

VARRAY

These are one-dimensional arrays with a fixed upper bound, specified at declaration.

They are useful when you know the maximum number of elements that will be stored in the array.

DECLARE

  TYPE num_array IS VARRAY(5) OF NUMBER;

  numbers num_array := num_array(10, 20, 30, 40, 50);

  total NUMBER := 0;

BEGIN

  -- Loop through the VARRAY

  FOR i IN 1..numbers.COUNT LOOP

    total := total + numbers(i);

  END LOOP;

  DBMS_OUTPUT.PUT_LINE('Total sum: ' || total);

END;

 

NESTED TABLE

These are one-dimensional arrays with no upper bounds.

They are declared using the TYPE statement and instantiated with the CREATE TYPE statement.

They behave similar to database tables and can be used in SQL operations.

DECLARE

  TYPE num_list IS TABLE OF NUMBER;

  numbers num_list := num_list(10, 20, 30, 40, 50);

  total NUMBER := 0;

BEGIN

  -- Loop through the nested table

  FOR i IN 1..numbers.COUNT LOOP

    total := total + numbers(i);

  END LOOP;

  DBMS_OUTPUT.PUT_LINE('Total sum: ' || total);

END;

 

ASSOCIATIVE ARRAY

These are similar to arrays in other programming languages but are indexed by a unique key rather than by consecutive integers.

They are declared using the TYPE statement and accessed using the key value.

DECLARE

  TYPE employee_salary IS TABLE OF NUMBER INDEX BY VARCHAR2(100);

  salaries employee_salary;

BEGIN

  salaries('John') := 50000;

  salaries('Alice') := 60000;

  salaries('Bob') := 55000;

  -- Accessing values

  DBMS_OUTPUT.PUT_LINE('John''s salary: ' || salaries('John'));

END;