EXTEND method

You can use the EXTEND method to append an element to the end of a variable-size array (or varray) or nested table.

A collection can be empty but not null. You can use the constructor function to make a collection empty or add elements to a null collection. For more information, see Collection constructor function.

Considerations for EXTEND are as follows:

• EXTEND appends a null element to a collection.

• EXTEND(n) appends n null elements to a collection.

• EXTEND(n,i) appends n copies of the ith element to a collection.

  Note

  Only EXTEND(n,i) is applicable to a collection with the NOT NULL constraint for elements.

EXTEND appends elements based on the internal size of a collection. In other words, if the DELETE method deletes an element but retains a placeholder for this element, EXTEND considers that this element still exists.

Here is an example:

obclient> DECLARE
  t nested_type:= nested_type('A', 'B', 'C');
BEGIN
  print_t(t);

  t.EXTEND(2,1);     -- Append two copies of the first element to the collection.
  print_t(t);

  t.DELETE(4);     -- Delete the fourth element.
  print_t(t);

  t.EXTEND;       -- Append a null element to the collection.
  print_t(t);

END;
/

Query OK, 0 rows affected
t.(1) = A
t.(2) = B
t.(3) = C
---
t.(1) = A
t.(2) = B
t.(3) = C
t.(4) = A
t.(5) = A
---
t.(1) = A
t.(2) = B
t.(3) = C
t.(5) = A
---
t.(1) = A
t.(2) = B
t.(3) = C
t.(5) = A
t.(6) = NULL
---

The preceding example declares a nested table variable, initializes and assigns values to three elements, and performs the following operations on the elements:

1. Append two copies of the first element to the collection.

2. Delete the fourth element.

3. Append a null element to the collection.

The print_nt stored procedure outputs the nested table variable after initialization and the EXTEND and DELETE operations.