Oracle PL/SQL Tutorial/PL SQL Operators/IS NULL
Версия от 13:45, 26 мая 2010; (обсуждение)
IS NULL
The IS NULL operator is used to test a NULL value.
Variables you declare in a PL/SQL block are also initially null, or have no value.
Variables remain null until your code specifically assigns a value to them.
The Syntax for IS NULL:
the_value IS [NOT] NULL