In the Excel table below, the 1^st column is the category; columns from the 2^nd to the 42^th are parallel columns of data items (below only shows some of the columns), where there are two types of values – X and null. Occasionally, there are duplicate values in a column under the same category.

Task: Group rows and combine values in each column in each group; only display one of the duplicate values if there are any.

Use SPL XLL to do this:

=spl("=?.group(~1).(g=~,(r1=~1).(g.(~(r1.#)).ifn()))",A2:E11)

group()function groups data and computes data in each group. ifn() function returns the first non-null member in the sequence; and it returns null if each member of the sequence is null. ~ is the current group; ~1 represents the 1^st row of the current group; and # is ordinal number of the current member.

Source:https://www.reddit.com/r/excel/comments/1clgby6/merging_rows_based_on_duplicates_in_one_column/