Examples Of Null; Quantified Comparison Predicates - HP Neoview SQL Reference Manual

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

Quantified Comparison Predicates

• "Considerations for ALL, ANY, SOME"
• "Examples of ALL, ANY, SOME"
A quantified comparison predicate compares the values of sequences of expressions to the values
in each row selected by a table subquery. The comparison operation is quantified by the logical
quantifiers ALL, ANY, or SOME.
row-value-constructor comparison-op quantifier table-subquery
row-value-constructor is:
(expression [,expression]...)
| row-subquery
comparison-op is:
= Equal
| <> Not equal
| != Not equal
| < Less than
| > Greater than
| <= Less than or equal to
| >= Greater than or equal to
quantifier is:
ALL | ANY | SOME
row-value-constructor
specifies the first operand of a quantified comparison predicate. The first operand can be
either of:
(expression [,expression ]...)
is a sequence of SQL value expressions, separated by commas and enclosed in parentheses.
expression cannot include an aggregate function unless expression is in a HAVING
clause. expression can be a scalar subquery (a subquery that returns a single row
consisting of a single column). See
row-subquery
is a subquery that returns a single row (consisting of a sequence of values). See
(page
ALL
specifies that the predicate is true if the comparison is true for every row selected by
table-subquery (or if table-subquery selects no rows), and specifies that the predicate
is false if the comparison is false for at least one row selected.
ANY | SOME
specifies that the predicate is true if the comparison is true for at least one row selected by
the table-subquery and specifies that the predicate is false if the comparison is false for
every row selected (or if table-subquery selects no rows).
242 SQL Language Elements
250).
"Expressions" (page 208).
"Subquery"