Compare with NULL value for non-equality : NULL « PL SQL Data Types « Oracle PL/SQL Tutorial






  1. Oracle PL/SQL Tutorial
  2. PL SQL Data Types
  3. NULL
SQL>
SQL> SET ECHO ON
SQL> SET SERVEROUTPUT ON
SQL> DECLARE
  2    a     INTEGER;
  3    b     BOOLEAN;
  4    n     INTEGER;     --this will be our null value.
  5  BEGIN
  6    a := 2;
  7
  8    IF a <> n THEN
  9      DBMS_OUTPUT.PUT_LINE('a <> n is true');
 10    ELSE
 11      DBMS_OUTPUT.PUT_LINE('a <> n is not true');
 12    END IF;
 13  END;
 14  /
a <> n is not true

PL/SQL procedure successfully completed.

SQL>
SQL>








21.24.NULL
21.24.1.All logical operations (including NOT) involving NULL always return NULL
21.24.2.variable:=nvl(value1,value2);
21.24.3.In PL/SQL the Boolean expression NULL=NULL evaluates to FALSE.
21.24.4.Short-circuit evaluation with conditional structures.
21.24.5.Compare with NULL value for equality
21.24.6.Compare with NULL value for non-equality
21.24.7.Compare NULL value and OR operator
21.24.8.Compare with NULL value and 'AND' operator
21.24.9.Compare Integer value with NULL value
21.24.10.Use IS NULL in IF statement
21.24.11.Use NVL in IF statement to deal with the NULL value comparison