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Hi all,
I’m having trouble blending three tables in Looker Studio (formerly Google Data Studio) using a helper months table as the join key. I keep running into an “Invalid argument type” error and can’t get the join to work as expected.
My setup:
Helper Months Table: Contains a single column with all months in my reporting range (e.g., 2023-01, 2023-02, etc.), formatted as Month Year.
Table A: Google Ads table with "Month" selected as the date dimension, but only includes months where there is data.
Table B: Another Google Ads table with "Month" selected, also only includes months where there is data.
I want to blend these so I get a complete list of months, with nulls where Table A or B have no data for a given month.
What I’ve tried:
Made the Helper Months table the leftmost table in the blend.
Attempted to join Table A and Table B to Helper Months using a full outer joins
Helper Months were Month Year.
Refreshed fields and rebuilt the blend multiple times.
The problem:
I keep getting an “Invalid argument type” error when I try to use the blend in a chart or table.
Questions:
Is there a best practice for joining tables like this when not all tables have every month in the range?
Any troubleshooting tips for resolving the “Invalid argument type” error in this context?
Screenshots of the two individual table/data I"m trying to join to one.
