oracle重载操作符的例子

转自：http://download.oracle.com/docs/cd/B13789_01/server.101/b10759/statements_6004.htm
Creating User-Defined Operators: Example
This example creates a very simple functional implementation of equality and then creates an operator that uses the function:
CREATE FUNCTION eq_f(a VARCHAR2, b VARCHAR2) RETURN NUMBER AS
BEGIN
IF a = b THEN RETURN 1;
ELSE RETURN 0;
END IF;
END;
/
CREATE OPERATOR eq_op
BINDING (VARCHAR2, VARCHAR2)
RETURN NUMBER
USING eq_f;