text: -- Copyright [1999-2015] Wellcome Trust Sanger Institute and the EMBL-European Bioinformatics Institute
  -- Copyright [2016-2018] EMBL-European Bioinformatics Institute
  -- 
  -- Licensed under the Apache License, Version 2.0 (the "License");
  -- you may not use this file except in compliance with the License.
  -- You may obtain a copy of the License at
  -- 
  --      http://www.apache.org/licenses/LICENSE-2.0
  -- 
  -- Unless required by applicable law or agreed to in writing, software
  -- distributed under the License is distributed on an "AS IS" BASIS,
  -- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  -- See the License for the specific language governing permissions and
  -- limitations under the License.
  
  alter table session add column end_time DATETIME after db_release;
  alter table session add column start_time DATETIME after db_release;
  
  drop view recent_session;
  drop view session_v;
  
  -- Most recent session
  CREATE VIEW recent_session AS
    SELECT s.*,
    	TIMEDIFF(end_time, start_time) AS duration 
     FROM session s, report r 
    WHERE s.session_id=(SELECT MAX(session_id) FROM session)
      AND r.last_session_id=s.session_id
      AND r.text LIKE '#%'
    GROUP BY r.last_session_id;
  
  -- View for derived data about sessions 
  
  CREATE VIEW session_v AS 
    SELECT s.*, 
    TIMEDIFF(end_time, start_time) AS duration 
    FROM session s, report r 
    WHERE s.session_id=r.last_session_id 
    AND r.text LIKE '#%' 
    GROUP BY r.last_session_id;
  
  