cross apply 셈플

select * 

  from oqm_qc_category A

 where start_dt in ( select MAX(x.start_dt)

                       from oqm_qc_category x

                      where A.qc_category_cd = x.qc_category_cd )

   --and qc_category_cd = 'M170604542'

SELECT TA.*

FROM oqm_qc_category TA

   CROSS APPLY (SELECT TOP 1 * FROM oqm_qc_category TB

                             WHERE TB.qc_category_cd = TA.qc_category_cd

                              AND TB.start_dt <= TA.start_dt

                              ORDER BY start_dt DESC) TT

--where    TA.qc_category_cd = 'M170604542'