User-Defined Operators

Like built-in operators, user-defined operators take a set of operands as input and return a result. However, you create them with the CREATE OPERATOR statement, and they are identified by names (e.g., MERGE). They reside in the same namespace as tables, views, types, and stand-alone functions.

Once you have defined a new operator, you can use it in SQL statements like any other built-in operator. For example, you can use user-defined operators in the select list of a SELECT statement, the condition of a WHERE clause, or in ORDER BY clauses and GROUP BY clauses. However, you must have EXECUTE privilege on the operator to do so, because it is a user-defined object.

For example, if you define an operator CONTAINS, which takes as input a text document and a keyword and returns 1 if the document contains the specified keyword, you can then write the following SQL query:

SELECT * FROM emp WHERE contains (resume, 'Oracle and UNIX') = 1;

See Also: "CREATE OPERATOR" and Oracle8i Data Cartridge Developer's Guide for more information on user-defined operators.