Comparison Conditions
Table 5–1 SQL Condition Precedence
Type of Condition |
Purpose |
|
|
SQL operators are evaluated before SQL |
See "Operator Precedence" on page 3-2 |
conditions |
|
|
|
=, !=, <, >, <=, >=, |
comparison |
|
|
IS [NOT] NULL, LIKE, [NOT] |
comparison |
BETWEEN, [NOT] IN, EXISTS, IS OF |
|
type |
|
|
|
NOT |
exponentiation, logical negation |
|
|
AND |
conjunction |
|
|
OR |
disjunction |
|
|
Comparison Conditions
Comparison conditions compare one expression with another. The result of such a comparison can be TRUE, FALSE, or UNKNOWN.
Note: Large objects (LOBs) are not supported in comparison conditions. However, you can use PL/SQL programs for comparisons on CLOB data.
Table 5–2 lists comparison conditions.
Table 5–2 |
Comparison Conditions |
|
Type of |
|
|
Condition |
Purpose |
Example |
|
|
|
= |
Equality test. |
SELECT * |
|
|
FROM employees |
|
|
WHERE salary = 2500; |
!=
^=
< >
¬=
Inequality test. Some forms of the inequality condition may be unavailable on some platforms.
SELECT *
FROM employees
WHERE salary != 2500;
5-4 Oracle9i SQL Reference
Comparison Conditions
Table 5–2 |
(Cont.) Comparison Conditions |
|
Type of |
|
|
Condition |
Purpose |
Example |
> |
"Greater than" and "less than" |
|
tests. |
< |
|
SELECT * FROM employees WHERE salary > 2500; SELECT * FROM employees WHERE salary < 2500;
>= |
"Greater than or equal to" and |
|
"less than or equal to" tests. |
<= |
|
SELECT * FROM employees WHERE salary >= 2500; SELECT * FROM employees WHERE salary <= 2500;
ANY
SOME
ALL
Compares a value to each value in |
SELECT * FROM employees |
|
a list or returned by a query. Must |
WHERE |
salary = ANY |
be preceded by =, !=, >, <, <=, >=. |
(SELECT salary |
|
Evaluates to FALSE if the query |
FROM |
employees |
returns no rows. |
WHERE |
department_id = 30); |
Compares a value to every value |
SELECT * FROM employees |
|
in a list or returned by a query. |
WHERE |
salary >= |
Must be preceded by =, !=, >, <, |
ALL ( |
1400, 3000); |
<=, >=. |
|
|
Evaluates to TRUE if the query returns no rows.
Simple Comparison Conditions
A simple comparison condition specifies a comparison with expressions or subquery results.
Conditions 5-5
Comparison Conditions
simple_comparison_condition::=
=
!=
^=
<>
expr |
expr |
>
<
>=
<=
=
,
!=
( |
expr |
) |
( |
subquery |
) |
^=
<>
expression_list::=
,
expr
,
( |
expr |
) |
If you use the lower form of this condition (with multiple expressions to the left of the operator), then you must use the lower form of the expression_list, and the values returned by the subquery must match in number and datatype the expressions in expression_list.
See Also:
■"Expression Lists" on page 4-16 for more information about combining expressions
■SELECT on page 18-4 for information about subqueries
5-6 Oracle9i SQL Reference
Comparison Conditions
Group Comparison Conditions
A group comparison condition specifies a comparison with any or all members in a list or subquery.
group_comparison_condition::=
= |
|
|
|
!= |
|
|
|
^= |
|
|
|
|
ANY |
|
|
<> |
|
|
expression_list |
expr |
SOME |
( |
) |
> |
|
|
subquery |
|
ALL |
|
|
< |
|
|
|
>= |
|
|
|
<= |
|
|
|
|
|
= |
|
|
’ |
|
, |
|
ANY |
|
|
|
|
!= |
|
|
expression_list |
( |
expr |
) |
SOME |
( |
) |
|
|
^= |
|
|
subquery |
|
|
|
ALL |
|
|
|
|
<> |
|
|
|
expression_list::=
,
expr
,
( |
expr |
) |
If you use the upper form of this condition (with a single expression to the left of the operator), then you must use the upper form of expression_list. If you use the lower form of this condition (with multiple expressions to the left of the operator), then you must use the lower form of expression_list, and the expressions in each expression_list must match in number and datatype the expressions to the left of the operator.
Conditions 5-7