dropped anchor rows with non-null recursion query

CREATE TABLE `purchases` (

  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,

  `pdate` date NOT NULL,

  `quantity` int(10) unsigned NOT NULL,

  `p_id` int(10) unsigned NOT NULL,

  PRIMARY KEY (`id`)

) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=latin1;

insert into purchases(pdate, quantity, p_id) values ('2014-11-01',5 ,1),('2014-11-03', 3 ,1), ('2014-11-01',2 ,2),('2014-11-03', 4 ,2);

CREATE TABLE `expired` (

  `edate` date NOT NULL,

  `quantity` int(10) unsigned NOT NULL,

  `p_id` int(10) unsigned NOT NULL,

  PRIMARY KEY (`edate`,`p_id`)

) ENGINE=InnoDB DEFAULT CHARSET=latin1;

insert into expired values ('2014-11-12', 5 ,1),('2014-11-08', 1 ,2);

with recursive expired_map as (

   select edate AS expired_date,

          CAST(NULL AS date) AS purchase_date,

          0 AS quantity,

          e.p_id,

          (SELECT MAX(id)+1 FROM purchases p WHERE pdate <= edate AND p.p_id =p_id) AS purchase_processed,

          quantity AS unresolved

   FROM expired e

   UNION

   (     SELECT expired_date,

                pdate,

                IF(p.quantity < m.unresolved, p.quantity, m.unresolved),

                p.p_id,

                p.id,

                IF(p.quantity < m.unresolved, m.unresolved - p.quantity, 0)

         FROM purchases p

         JOIN expired_map m ON p.p_id = m.p_id

         WHERE p.id > 3000

   )

)

select  * from expired_map ;

+--------------+---------------+----------+------+--------------------+------------+

| expired_date | purchase_date | quantity | p_id | purchase_processed | unresolved |

+--------------+---------------+----------+------+--------------------+------------+

| 2014-11-08   | NULL          |        0 |    2 |                  5 |          1 |

| 2014-11-12   | NULL          |        0 |    1 |                  5 |          5 |

+--------------+---------------+----------+------+--------------------+------------+

with recursive expired_map as (

   select edate AS expired_date,

          CAST(NULL AS date) AS purchase_date,

          0 AS quantity,

          e.p_id,

          (SELECT MAX(id)+1 FROM purchases p WHERE pdate <= edate AND p.p_id =p_id) AS purchase_processed,

          quantity AS unresolved

   FROM expired e

   UNION

   (     SELECT expired_date,

                pdate,

                IF(p.quantity < m.unresolved, p.quantity, m.unresolved),

                p.p_id,

                p.id,

                IF(p.quantity < m.unresolved, m.unresolved - p.quantity, 0)

         FROM purchases p

         JOIN expired_map m ON p.p_id = m.p_id

         WHERE p.id < m.purchase_processed AND m.unresolved > 0

         ORDER BY p.id DESC

         LIMIT 1

   )

)

select  * from expired_map ;

+--------------+---------------+----------+------+--------------------+------------+

| expired_date | purchase_date | quantity | p_id | purchase_processed | unresolved |

+--------------+---------------+----------+------+--------------------+------------+

| 2014-11-08   | NULL          |        0 |    2 |                  5 |          1 |

| 2014-11-08   | 2014-11-03    |        1 |    2 |                  4 |          0 |

+--------------+---------------+----------+------+--------------------+------------+