EXTEND method

The EXTEND method appends elements to the end of a VARRAY or nested table.

A collection can be empty but cannot be NULL. You can use a constructor to make a collection empty or to append elements to a NULL collection. For more information, see Collection constructors.

The EXTEND method is used as follows:

• EXTEND appends a NULL element to the collection.

• EXTEND(n) appends n NULL elements to the collection.

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

  Note

  Only EXTEND(n, i) can be used for collections with elements that have a NOT NULL constraint.

The EXTEND method operates based on the internal size of the collection. That is, if DELETE removes an element but retains a placeholder for it, EXTEND considers the element to still exist.

Here are some examples:

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

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

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

  t.EXTEND;       -- Appends 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 and initializes it with three elements. It then performs the following operations:

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

2. Deletes the fourth element.

3. Appends a NULL element to the collection.

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