oracle function

1CREATE OR REPLACE FUNCTION to_date_check_null(dateString IN VARCHAR2, 
2	dateFormat IN VARCHAR2) RETURN DATE IS
3BEGIN 
4    IF dateString IS NULL THEN
5        return NULL;
6    ELSE
7        return to_date(dateString, dateFormat);
8    END IF;
9END;

1CREATE [OR REPLACE] FUNCTION function_name
2   [ (parameter [,parameter]) ]
3
4   RETURN return_datatype
5
6IS | AS
7
8   [declaration_section]
9
10BEGIN
11   executable_section
12
13[EXCEPTION
14   exception_section]
15
16END [function_name];