How to search records based on date range for other matching data I have below records in table

APP_No Stage Start_Date End_Date 
A123   L1    01-01-19 02-01-19 
A123   D1    01-03-19 05-03-19 
A345   L1    01-01-19 02-01-19 
A345   D1    01-03-19 05-03-19


I want to search records for stage D1 for the month of Mar19 but this should include data for L1 stage also, since related app ID fall between same Mar19 date range. 
I have used condition in where clause as : trunc(Col_Name) BETWEEN trunc (sysdate, 'mm')/current month/ AND SYSDATE

Please help with solution
Try ans use EXISTS to get all records where another (or the same for that matter) exists with the same app ID, a stage of 'D1' and the start date or the end date in march.

Assuming you're on Oralce, this could look like this:

SELECT *
       FROM elbat t1
       WHERE EXISTS (SELECT *
                            FROM elbat t2
                            WHERE t2.app_no = t1.app_no
                                  AND stage = 'D1'
                                  AND (t2.start_date &gt;= to_date('2019-03-01', 'yyyy-mm-dd')
                                       AND t2.start_date &lt; to_date('2019-04-01', 'yyyy-mm-dd')
                                        OR t2.end_date &gt;= to_date('2019-03-01', 'yyyy-mm-dd')
                                           AND t2.end_date &lt; to_date('2019-04-01', 'yyyy-mm-dd')));