SQL Experts - Need help identifying dates ranges when Direct Reports Exist

Does anyone have SQL lying around that can merge a table of dates into a reduced data set that represents a blend of the dates ? See below.

DROP TABLE dummydates_tbl;CREATE TABLE dummydates_tbl (EMPID NUMBER,MANAGERID NUMBER,STARTDATE DATE,ENDDATE DATE);INSERT INTO dummydates_tbl values (9769,1234,to_date('01-JAN-2012','DD-MON-YYYY'),to_date('30-JAN-2012','DD-MON-YYYY'));INSERT INTO dummydates_tbl values (5512,1234,to_date('25-JAN-2012','DD-MON-YYYY'),to_date('25-FEB-2012','DD-MON-YYYY'));INSERT INTO dummydates_tbl values (9769,1234,to_date('10-MAR-2012','DD-MON-YYYY'),to_date('30-JUN-2012','DD-MON-YYYY'));INSERT INTO dummydates_tbl values (8853,1234,to_date('10-MAR-2012','DD-MON-YYYY'),to_date(