Blended source doesn't show data when 1 source does not have data

Looker Q&A Looker Studio
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1

Hi all,

I have two data sources with data separated by month.

  • Left Table Source 1 has data in Jan & Feb.
    -     Right Source 2 does not have data in those months..

I have chosen Left Outer join so it would display all data from Source 1 and additional from Source 2.

  • When pulling up the data, the table shows on Dimension Date “Null” for the months that Source 2 does not have data.
  • The sum function of both source 1 and 2 shows “Null” as well.

How can I correct this situation that the chart still shows the data present in Source 1 even thought Source 2 lacks that?

However, when I

2

Hi,

You’re actually very close, this is normal and expected behaviour in Looker Studio.
When you use a Left Outer Join, the join keeps all the records from your left table (Source 1) and only brings in matching records from your right table (Source 2). So, if Source 2 doesn’t have data for certain months, those fields will appear as Null.

That’s why your table shows “Null” for Date and sums when Source 2 is missing data. It doesn’t mean the join failed, it just means there’s no corresponding data on the right side.
To fix how it looks, create a calculated field using something like:

SUM(IFNULL(Sales, 0))

This ensures that Null values are treated as 0 during aggregation, allowing your totals from Source 1 to display correctly even when Source 2 has no data. In short, your setup is correct, this is expected behaviour for Left Outer Joins when one source doesn’t contain matching records.

1 Like
3

Hi,

Thank you for your response as it is very helpful.

How would the IFNULL function work for missing months? Now it displays the missing months as null as well.

4

Hi,

For missing months, you can apply the IFNULL() function to substitute null values with a meaningful label, ensuring your report remains clear and consistent. This way, instead of showing null for months without data, a descriptive placeholder will appear. However, if those months are completely absent (no rows exist for them), you’ll need to ensure your date dimension includes all months.

I hope this helps, if not, feel free to share a snapshot of your data so I can provide a more precise and tailored explanation.