Comparing with NULL : IF « PL SQL Statements « Oracle PL/SQL Tutorial

SQL>
SQL>
SQL> declare
  2      v NUMBER;
  3  begin
  4      if v = 1 then
  5          DBMS_OUTPUT.put_line('Equal to 1');
  6      elsif v!= 1 then
  7          DBMS_OUTPUT.put_line('Not equal to 1');
  8      elsif v = v then
  9          DBMS_OUTPUT.put_line('Equal to itself');
 10      else
 11          DBMS_OUTPUT.put_line('Undefined result');
 12      end if;
 13      v:=v+1;
 14      DBMS_OUTPUT.put_line('New value: <'||v||'>');
 15  end;
 16  /
Undefined result
New value: <>

PL/SQL procedure successfully completed.

SQL>
SQL>

22.1.IF
	22.1.1.	Conditional Logic
	22.1.2.	Handling conditions
	22.1.3.	A Simple Condition Statement
	22.1.4.	A Simple Condition Statement with BOOLEAN variable
	22.1.5.	The IF...THEN...ELSE Statement
	22.1.6.	Use IF THEN ELSE IF
	22.1.7.	IF...ELSE statements
	22.1.8.	Using an ELSIF Statement
	22.1.9.	IF..ELSIF ladder
	22.1.10.	Block IF statement
	22.1.11.	IF with ELSE
	22.1.12.	The Syntax for IF...ELSIF
	22.1.13.	ELSIF Ladder
	22.1.14.	The Syntax for Nested IF Statements
	22.1.15.	Use if with 'IN'
	22.1.16.	Three valued comparison
	22.1.17.	JUMP out of a IF statement with goto
	22.1.18.	Comparing with NULL
	22.1.19.	If block statement
	22.1.20.	Create a function and call it in an if statement
	22.1.21.	PLW-06002: Unreachable code