Duplicates

Finding

Removing

Delete duplicate rows (or cells) from a sheet
Make a copy first (as you cannot use the Undo ?? Check)
Lets specify which columns should be checked for duplicate information
Choose the columns you want to consider.
If you want to remove rows where both column1 and column2 are the same, check both these columns in the dialog box
For a unique list of items only select that particular column.
It will report that "n" duplicates were removed and "m" records remain.

removes from multiple columns =INDEX(tbl_text, MIN(IF(COUNTIF($B$12:B12, tbl_text)=0, ROW(tbl_text)-MIN(ROW(tbl_text))+1)), MATCH(0, COUNTIF($B$12:B12, INDEX(tbl_text, MIN(IF(COUNTIF($B$12:B12, tbl_text)=0, ROW(tbl_text)-MIN(ROW(tbl_text))+1)), , 1)), 0), 1)

Unique Values - returns a count of unique values
={sumproduct(( 1/countif(A1:D3, A1:D3))}

Unique Values - returns the unique values
={if(countif(A1:D3,A1:D3)<1,A1:D3)}

UNIQUE Function

(Added in 2021)