sql query: For each record where is_queue_empty=1 and queue_name is empty get immediate next record by timestamp where …

How can we construct sql query with following constraint.

For each record where is_queue_empty=1 and queue_name is empty get im开发者_StackOverflowmediate next record by timestamp where is_queue_empty=0 and queue_name can or cannot be empty for same session-id and request-id.

Table has following columns:

session_id,request_id,queue_name ,is_queue_empty,timestamp,queue_tag,tab_name.

What I have do far is this which is incorrect:

SELECT x.tab_name,
       x.is_queue_empty,
       x.SESSION_ID, 
       x.request_ID,
       x.TO_CHAR(DATETIME, 'YYYY/MM/DD HH24:MI:SS') timestamp,

       y.tab_name,y.queue_name,y.is_queue_empty

FROM   queue_data AS x
WHERE  
        timesttamp < TO_DATE('2011/02/30')
       AND timestamp >= TO_DATE('2011/01/01')

      AND is_queue_empty=1

    AND timestamp < (select TO_CHAR(timestamp, 'YYYY/MM/DD HH24:MI:SS') as timestamp from queue_data as Y where x.session_id = y.session_id and x.request_id=y.request_id and y.is_queue_empty=0 order by y.timestamp asc limit 1 )

select a.session_id,a.request_id,a.timestamp,a.queue_tag,
  b.*
from
(
    select session_id,request_id,timestamp,queue_tag,
     (select min(b.timestamp)
      from tbl b
      where a.session_id=b.session_id
        and a.request_id=b.request_id
        and b.timestamp > a.timestamp
        and b.is_queue_empty=0) nextrec
    from tbl a
    where is_queue_empty=1 and nullif(queue_name,'') is null
) a
left join tbl b on a.session_id=b.session_id
               and a.request_id=b.request_id
               and a.nextrec = b.timestamp

Note:

1. tbl is the name of the table
2. Assuming timestamp is unique within a session_id,request_id combo