SQL query

CREATE TABLE test (Person VARCHAR(20),  Action VARCHAR(10), [Date]   DATE)
INSERT INTO test
VALUES      ('MAX','Sale','20100720'),
            ('MAX','Sale','20101026'),
            ('MAX','Sale','20101103'),
            ('MAX','Sale','20110401'),
            ('MAX','No Sale','20110528'),
            ('MAX','Sale','20110613'),
            ('MAX','Sale','20110711'),
            ('MAX','Sale','20110819'),
            ('MAX','No Sale','20111001'),
            ('MAX','No Sale','20111209'),
            ('MAX','Sale','20120201'),
            ('MAX','No Sale','20120201'),
            ('MAX','Sale','20120207'),
            ('MAX','Sale','20120213'),
            ('MAX','No Sale','20130706');
;with mycte as
                        (  
                        select *, row_number() Over(order By [Date],Action Desc) rn1
                        , row_number() Over(partition by  Action order By Date, aCTION desc) rn2 
                        , row_number() Over(order By [Date],Action DESC ) - row_number() Over(Partition by  Action Order By [Date] ) rn3 
                        from test)
        , mycte2 as 
                         ( Select *,row_number() Over(partition by  rn3 order By ACTION DESC,[Date]) rn4
                         , row_number() Over(partition by  rn3 order By Action  ) rn5 
                         from  mycte )
                SELECT Person,Action,[Date],'Y' AS flag
        FROM   mycte2
        WHERE  rn4 = 1  OR rn5 = 1
        ORDER  BY [Date], ACTION DESC 
        
DROP TABLE test 
/*
Person  Action  Date    flag
MAX     Sale    2010-07-20      Y
MAX     No Sale 2011-05-28      Y
MAX     Sale    2011-06-13      Y
MAX     No Sale 2011-10-01      Y
MAX     Sale    2012-02-01      Y
MAX     No Sale 2012-02-01      Y
MAX     Sale    2012-02-07      Y
MAX     No Sale 2013-07-06      Y
*/