Oracle9i SQL Reference Release 1 (9.0.1) Part Number A90125-01 |
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Operators, 6 of 6
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. They reside in the same namespace as tables, views, types, and standalone 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 INCLUDES
, 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 includes (resume, 'Oracle and UNIX') = 1;
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