Scorecard chart with CountDistinct returns incorrect results

[ChrisRode]

Hi all

We're using Scorecards to show a Distinct Count of a particular datasource value for "Last Month". What we have found is that it consistently shows a slightly inflated value from what I get if I run the datasource query myself.

This seems to only occur for a count distinct, not for a sum

Any help you can lend would be greatly appreciated

[a_aleinikov]

Hi @ChrisRode ,

Yes, this is a known issue — in Looker Studio, CountDistinct on aggregated or blended data can overcount, especially if the data isn’t fully deduplicated upstream.

A few things to check or try:

• Make sure the data source returns deduplicated rows before reaching Looker Studio.

• Use a custom SQL query or a pre-aggregated table to calculate the distinct count upstream.

• In some cases, switching from blended data to a single-source connection can improve accuracy.