Project Planning

/*
First, extract the start_date which not the same with the end_date and end_date which not the same with the start_date.
Then combine this two information, with the requirement that start_date < end_date and use the MIN() function to extract the minimum end_date for each start_date.
Then sort it by the different days between start and end date and by the start date
*/

WITH A AS
(SELECT Start_Date
   FROM Projects
   WHERE Start_Date NOT IN (SELECT End_Date FROM Projects))
        
, B AS
(SELECT End_Date
   FROM Projects
   WHERE End_Date NOT IN (SELECT Start_Date FROM Projects))
 
, NP AS
(SELECT Start_Date, MIN(End_Date) AS End_date
FROM A,B
WHERE Start_Date < End_Date
GROUP BY Start_Date)

SELECT *
FROM NP
ORDER BY DATEDIFF(day, Start_Date, End_Date), Start_date;