Difference between empty plsql record and null plsql record

Question

Hi there,
I am kinda getting confused with empty plsql record and null plsql record.
How do I assign plsql record to be empty and to be null?
create type emp_obj as object (enum number, ename varchar2);
CREATE OR REPLACE TYPE emp_type AS TABLE OF emp_obj;
Thanks

Answer 1

First of all, do not use term PL/SQL record in this context. Record type in PL/SQL is completely different from object type. Secondly, there are 2 states of a nested table:
1. Unintialized:
SQL> create or replace
  2    type emp_obj_type as object(enum number, ename varchar2(10));
  3  /
Type created.
SQL> create or replace
  2    type emp_tbl_type as table of emp_obj_type
  3  /
Type created.
SQL> declare
  2      v_emp_tbl emp_tbl_type;
  3  begin
  4      v_emp_tbl.extend;
  5  end;
  6  /
declare
ERROR at line 1:
ORA-06531: Reference to uninitialized collection
ORA-06512: at line 4
SQL> 2 Empty:
SQL> set serveroutput on
SQL> declare
  2      v_emp_tbl emp_tbl_type := emp_tbl_type();
  3  begin
  4      dbms_output.put_line('Nested table v_emp_tbl has ' || v_emp_tbl.count || ' element(s).');
  5  end;
  6  /
Nested table v_emp_tbl has 0 element(s).
PL/SQL procedure successfully completed.
SQL> NULL aplies to nested table element, not to nested table itself:
SQL> declare
  2      v_emp_tbl emp_tbl_type := emp_tbl_type();
  3  begin
  4      v_emp_tbl.extend;
  5      if v_emp_tbl(1) is null
  6        then
  7          dbms_output.put_line('Nested table v_emp_tbl first element is NULL.');
  8      end if;
  9  end;
10  /
Nested table v_emp_tbl first element is NULL.
PL/SQL procedure successfully completed.
SQL> SY.