SQL/MX 2.x Reference Manual (H06.04+)

SQL/MX Language Elements
HP NonStop SQL/MX Reference Manual—540440-003
6-96
NULL Predicate
Considerations for NULL
Summary of NULL Results
Let rvc be the value of the row-value-constructor. This table summarizes the
results of NULL predicates. The degree of a rvc is the number of values in the rvc.
Note that the rvc IS NOT NULL predicate is not equivalent to NOT rvc IS NULL.
Examples of NULL
•
Find all rows with null in the SALARY column:
salary IS NULL
•
This predicate evaluates to true if the expression (PRICE + TAX) evaluates to null:
(price + tax) IS NULL
•
Find all rows where both FIRST_NAME and SALARY are null:
(first_name, salary) IS NULL
Expressions
rvc IS
NULL
rvc IS
NOT NULL
NOT rvc IS
NULL
NOT rvc IS
NOT NULL
degree 1: null TRUE FALSE FALSE TRUE
degree 1: not null FALSE TRUE TRUE FALSE
degree>1: all null TRUE FALSE FALSE TRUE
degree>1: some null FALSE FALSE TRUE TRUE
degree>1: none null FALSE TRUE TRUE FALSE