Fill values that don't exist with values from another column

[ramasaurio]

I have a table with a column with missing values, I want to fill those missing values with a column in another table.

I created this sample data as an example (sample_data.pbix) : 

Table A

date	value_A
Friday, 13 September, 2024	1623
Sunday, 15 September, 2024	9584

Table B

date	value_B
Friday, 13 September, 2024	5483
Saturday, 14 September, 2024	9084
Sunday, 15 September, 2024	1234

dates

date	week_id
Friday, 13 September, 2024	37
Saturday, 14 September, 2024	37
Sunday, 15 September, 2024	38

The relationship between the tables are as follows using "date" as the key between them.

what I need to do is create a column with the values of column "value_A" from Table A, and fill the missing values (in this case the value for September 14th) with the values of "value_B". In this case, the column should have the values: 1623, 9084, 9584, for each date respectively.

I'm not really sure how to determine when a row in Table A doesn't exist. Table dates has the complete set of dates but I should leave that table intact. Table B may or may not have all the values, so I should leave a 0 if both Table A and Table B don't have that particular date.

Does anyone have directions for me to achieve this?

Thanks in advance.

[lbendlin · Accepted solution]

Read about COALESCE

[ramasaurio]

Perfection.

Thank you!

Edit:

The subtotals looks off, it show the same value as value_A. I'll play with it a bit more and see how it works.