How to use vlookup duplicate values

Answer

VLOOKUP is designed to return the first matching value it finds in a column. Handling duplicate values requires specific approaches because VLOOKUP alone cannot return multiple matches at once.

1. Using VLOOKUP to Return the First Match

To return the first occurrence of a value in a dataset:

1. Select the cell where you want the result.

2. Enter the formula: 

   =VLOOKUP(lookup_value, table_array, col_index_num, FALSE)

• lookup_value is the value to find.

• table_array is the range of cells containing the data.

• col_index_num is the column number from which to return the value.

• FALSE ensures an exact match.

Example: To find the first sales amount for the employee "John" in a sales table where names are in column A and sales in column B: 

=VLOOKUP("John", A2:B10, 2, FALSE)

This formula will return the first sales amount for John.

2. Handling Multiple Duplicate Matches

To extract all duplicate values, combine VLOOKUP with helper columns or use array formulas:

Method 1: Using Helper Column

1. Add a helper column to create a unique identifier. For example, in column C:

   =A2 & COUNTIF($A$2:A2, A2)

This appends a count to each duplicate, making each entry unique.

2. Use VLOOKUP with the helper column. For example, to find the second occurrence of "John":

   $=VLOOKUP("John2",C2:B10,2,FALSE)$
   

Method 2: Using INDEX and SMALL for Multiple Matches

1. Enter the formula to retrieve all occurrences of a value:

   $=INDEX(B\$2:B\$10,SMALL(IF(A\$2:A\$10="John",ROW(A\$2:A\$10)-ROW(A\$2)+1),ROW(1:1)))$
   

2. Press Ctrl+Shift+Enter to make it an array formula in versions prior to Excel 365. In Excel 365, pressing Enter is sufficient.

3. Drag the formula down to get all duplicate matches.

Explanation:

• $IF(A\$2:A\$10="John",ROW(A\$2:A\$10)-ROW(A\$2)+1)$creates an array of row numbers where the value matches.

• $SMALL(...,ROW(1:1))$retrieves the nth occurrence.

• $INDEX$ Returns the corresponding value from column B.

3. Notes for Mac and Windows

• Formula syntax is the same on Mac and Windows.

• Array formulas in Mac versions of Excel may require Command+Shift+Enter instead of Ctrl+Shift+Enter in older Excel versions.

4. Best Practices

1. Sort your data before using VLOOKUP if order matters.

2. Use helper columns for large datasets to improve performance.

3. Consider using FILTER Excel 365 for an easier solution: 

   =FILTER(B2:B10, A2:A10="John")

This formula automatically returns all matching values without complex array formulas.

Using these methods ensures you can accurately retrieve values from datasets with duplicates.

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