TRIM method

You can use the TRIM method to trim elements from the end of a variable-size array (or varray) or nested table.

Considerations for TRIM are as follows:

• TRIM will trim one element from the end of a collection. Therefore, the collection must contain at least one element. Otherwise, the predefined exception SUBSCRIPT_BEYOND_COUNT will be raised.

• TRIM(n) will trim n elements from the end of a collection. Therefore, the collection must contain at least n elements. Otherwise, the predefined exception SUBSCRIPT_BEYOND_COUNT will be raised.

TRIM trims 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, TRIM considers that this element still exists. Therefore, you can use TRIM to trim a deleted element.

PL does not retain placeholders for trimmed elements. Therefore, trimmed elements are not counted in the internal size of a collection, and you cannot recover trimmed elements by assigning valid values to them.

Here is an example:

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

  t.TRIM;          -- Trim the last element.
  print_t(t);

  t.DELETE(3);     -- Delete the third element.
  print_t(t);

  t.TRIM(2);       -- Trim the last two elements.
  print_t(t);

END;
/
Query OK, 0 rows affected

t.(1) = A
t.(2) = B
t.(3) = C
t.(4) = D
t.(5) = E
t.(6) = F
---
t.(1) = A
t.(2) = B
t.(3) = C
t.(4) = D
t.(5) = E
---
t.(1) = A
t.(2) = B
t.(4) = D
t.(5) = E
---
t.(1) = A
t.(2) = B
---

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

1. Trim the last element.

2. Delete the fourth element.

3. Trim the last two elements.

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