If you want to search for part of one cell, you can use find
formula which search for given text within cell value find(text,withintext)
and it return index that the text start with and error if not.
And if you need your process to be work line by line,
the final formula ( for row2 of sheet2 column A ) would look like this:
=IF(AND(NOT(ISERROR(FIND(Sheet1!A2,Sheet2!D2))),Sheet1!A2<>""),Sheet1!A2,"")
if row2 of column A of sheet1 is not empty and is found (no error returned);the value of sheet1 column A returned otherwise empty will returned.
Hope that was useful.
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