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In PL/SQL we have a varray named data structure which is a variable size array which can be used to store a fixed size of data elements of same type, sequentially, where the number of elements can vary from zero (empty) to the declared maximum size.

A varray stores data in contiguos memory locations where the first element is stored at the lowes address location and the last element is stored at the highest address location.

To access the data elements stored in a varray type variable, we use the syntax variable_name(index) where index starts from 1 for the first element and goes upto the current upper bound of elements which means the number of elements that exists at that given point(not the maximum size of the array).

The upper bound keeps on changing as you add or remove elements from an array, but it cannot exceed the maximum size of the array.

Whenever you store and fetch back a varray from the database, its indexes and the element order remain stable.

For example, in the diagram below we have a varray Marks of size 8 and 5 data elements are stored in it.

PL/SQL varray collection

In the above varray Marks if you want to access the second element, all you need to do it Marks(2)

The database stores a varray variable as a single object. If a varray variable is less than 4 KB, it resides inside the table of which it is a column; otherwise, it resides outside the table but in the same tablespace.

Declaring a Varray Type

We can declare a new varray type using the TYPE statement inside the PL/SQL block.

TYPE varr_type_name IS VARRAY(n) of <element_type>

For example,

TYPE snamearray IS VARRAY(10) OF VARCHAR2(20); 
Type sagearray IS VARRAY(10) OF INTEGER;

In the example above we have initialized two varray types, first one can hold 10 elements of type varchar and the second one can hold 10 elements of type integer.

An uninitialized varray variable is a null collection. You must initialize it, either by making it empty or by assigning a non-NULL value to it.

Time for an Example!

In the program below, we have used varray:

   type snamesarray IS VARRAY(5) OF VARCHAR2(10); 
   type smarks IS VARRAY(5) OF INTEGER; 
   snames namesarray := namesarray('John', 'Adam', 'Elly', 'Kate', 'Ron'); 
   marks smarks := smarks(42, 88, 62, 89, 97); 
   no_of_students := snames.count; 
   dbms_output.put_line('Total '|| no_of_students || ' Students'); 
   FOR i in 1 .. no_of_students LOOP 
      dbms_output.put_line('Student: ' || snames(i) || ' 
      Marks: ' || marks(i)); 

Total 5 Students Student: John Marks: 42 Student: Adam Marks: 88 Student: Elly Marks: 62 Student: Kate Marks: 89 Student: Ron Marks: 97 PL/SQL procedure successfully completed.

As you can see in the example above, we have declared two varray types one for storing student names and another on for storing student's marks.

And then we have used them in our PL/SQL block for storing student names and student marks.