Null Predicate

Wed, 03/04/2009 - 20:02 |  hdanzl

Specify a test for a null value.


Syntax

<null predicate> ::=
<null predicate part 2> ::= IS [ NOT ] NULL


Notes

♦ The degree of the row value predicand shall be 1.
♦ IS NULL evaluates to TRUE if the row value is null, else to FALSE.
♦ IS NOT NULL evaluates to TRUE if the row value is different from null, else to FALSE.


Examples

1) The following example selects students who don't take any courses:

       SELECT studentID, studentName

       FROM students s

       left join enrolls e ON e.studentID = s.studentID

       WHERE e.studentID IS NULL


Conformance

SQL:2003 standard

-

-

Core SQL

Feature F481 "Expanded NULL predicate"
‹ Like PredicateupQuantified Comparison Predicate ›
Print this chapter |  Login or register to post comments |  Send to friend |  PDF version |  metadata Tags:
Home | Site Contents | Documentation | NexusDB Manual V4 | SQL Reference | Predicates

Powered by Drupal and Drupal Theme created with Artisteer.