Removing Duplicate Data with LOD Calculations

Published: 22 Dec 2015
Last Modified Date: 02 Jun 2023

Question

How to use LOD calculations to delete duplicated data when joining two or more tables.

Environment

Tableau Desktop
Table joins

Answer

Use a FIXED expression to remove the duplicate data.

It is necessary to know which dimension in the data source is unique for each row value, or the combination of dimensions. For example, if the measures on Table A have a unique row identifier based on Date/Time, use that dimension to remove duplicate values.

Once the necessary dimension or dimensions are found, use an LOD calculation to remove the duplicate values.

For example:
{Fixed [Unique Dimension]: MIN([Measure])}

If the table's rows are uniquely identified by a combination of multiple dimensions, use a calculation similar to the following where dimensions 1 through 3 make up a unique identifier:
{Fixed [Dimension 1],[Dimension 2], [Dimension 3]: MIN([Measure])}

To view these steps in action, see the video below:

Additional Information

This solution will also work to remove duplicates created by appending data to an extract, where a row may be duplicated if the row is in both the original extract and the appended data.

Create Level of Detail Expressions in Tableau