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Requirement: In table which has row numbers and need to fill null value with previous non null value.

Solution: Using Cross Apply and Top 1 row

Tsql Syntax (Gen):

Select Coalesce(Tbl1.<Column1>,Tbl2.<Column1>) GTIN,Tbl1.* From Tbl Tbl1 --Coalesce would fetch first non Null Value
Cross Apply (Select top 1 <Column2> from Tbl Tbl2 -- Top 1 value would get only 1 record
             Where Tbl2.Row_Num <= Tbl1.Row_Num and <Column1> is not null --Row_N is row_number
             Order by Row_Num Desc) QE2 --Order by Row_Namber