Comparison predicate 

The comparison predicate is used to compare two values. The left hand side operand has to be a value expression whereas the right hand sight operand can additionally be a dynamic parameter specification or a scalar sub-query.

Syntax

<comparison predicate> ::=            <value expression>                  <comparison operator>                       ( <value expression>                       | <dynamic parameter specification>                       | <scalar subquery> ). <comparison operator> ::= '<' | '=' | '>' | '<=' | '<>' | '>='.

 

The data types of the two <value expression>s in the <comparison predicate> must be comparable. For more information about comparable types, see Open SQL Data Types in the Development Manual.

If either of the <value expression>s is NULL, the result of the <comparison predicate> is unknown.

It is not possible to test for NULL values with a comparison predicate. You may wish to use a null predicate instead.

Examples

SELECT * FROM a WHERE c > 0

Comparison predicate. This SELECT yields all rows from table a where the column a.c has a value larger than 0.

DELETE FROM employees WHERE employee_id = ?

Dynamic Parameter in Comparison Predicate. All employees with the employee_id equal to a given parameter are delete from the table employees.