I have the following table and I'm trying to detect products that have a break in its spans.

Product     | unit_Cost | price start date |    price end date
--------------------------------------------------------------------------
product 1     15.00         01/01/2011      03/31/2011
product 1     15.00         04/01/2011      06/31/2011
product 1     15.00         07/01/2011      09/31/2011
product 1     15.00         10/01/2011      12/31/2011

product 2     10.00         01/01/2011      12/31/2011

product 3     25.00         01/01/2011      06/31/2011
product 3     25.00         10/01/2011      12/31/2011

So here I want it to report back product3 because we are missing the span

07/01/2011 - 09/31/2011

Any ideas on how I can do this?

EDIT: Oracle Ver: 10g

Create Table Statement

CREATE TABLE Sandbox.TBL_PRODUCT
(
  PRODUCT_ID        VARCHAR2(13 BYTE),   
  PRODUCT           VARCHAR2(64 BYTE),
  UNIT_COST         NUMBER,
  PRICE_START_DATE  DATE,
  PRICE_END_DATE    DATE
)

EDIT 2 start dates and end dates cannot overlap

EDIT 3 a span can be any two dates as long as price_end_date >= price_start_date. Equal is included since a product can be on sale for one day.

Try this (using LEAD analytic function):

SELECT *
  FROM (
                SELECT a.*, LEAD(price_start_date,1,NULL) OVER(PARTITION BY product ORDER BY price_end_date) next_start_date 
         FROM Product a
       )
WHERE (price_end_date + 1)<> next_start_date

Example with Setup

        CREATE TABLE PRODUCT
          (
            PRODUCT   VARCHAR2(100 BYTE),
            UNIT_COST NUMBER,
            START_DATE DATE,
            END_DATE DATE
          );

        INSERT INTO Product VALUES('product 1','15.00',TO_DATE('01/01/2011','MM/DD/RRRR'),TO_DATE('03/31/2011','MM/DD/RRRR'));
        INSERT INTO Product VALUES('product 1','15.00',TO_DATE('04/01/2011','MM/DD/RRRR'),TO_DATE('06/30/2011','MM/DD/RRRR'));
        INSERT INTO Product VALUES('product 1','15.00',TO_DATE('07/01/2011','MM/DD/RRRR'),TO_DATE('09/30/2011','MM/DD/RRRR'));
        INSERT INTO Product VALUES('product 1','15.00',TO_DATE('10/01/2011','MM/DD/RRRR'),TO_DATE('12/31/2011','MM/DD/RRRR'));
        INSERT INTO Product VALUES('product 2','10.00',TO_DATE('01/01/2011','MM/DD/RRRR'),TO_DATE('12/31/2011','MM/DD/RRRR'));
        INSERT INTO Product VALUES('product 3','25.00',TO_DATE('01/01/2011','MM/DD/RRRR'),TO_DATE('06/30/2011','MM/DD/RRRR'));
        INSERT INTO Product VALUES('product 3','25.00',TO_DATE('10/01/2011','MM/DD/RRRR'),TO_DATE('12/31/2011','MM/DD/RRRR'));

SELECT *
  FROM (
                SELECT a.*, LEAD(start_date,1,NULL) OVER(PARTITION BY product ORDER BY start_date) next_start_date 
                 FROM Product a
              )
WHERE (end_date + 1)<> next_start_date

EDIT:Updated the query to consider the next start_date and current end_date to avoid issues with the distribution of the data.