One of my users sent me a list of ISBNs that he'd like to track sales for. I made this the starting table in the Metabase query editor. I then did a lookup to a sales table by ISBN. Then a second lookup to title information, also by the ISBN. As it is a daily sales file, I want to summarize the totals.
Metabase got a little unusual on me when I went to summarize, keeping in mind that the values to be summed are on the looked up table, not the first table. The usual sum and average functions weren't in the list of choices. I could do a workaround by creating a custom field, but that is kind of the long way around and shouldn't be necessary. I then tried inverting the question, starting with the sales file, then doing a lookup to the specific list of ISBNs. Voila, the functions magically reappeared.
So apparently, if there isn't a numeric field in the initial table, Metabase suppresses the options when summarizing, even if the fields to be summarized are in a joined table. Is this a bug or a feature? I would place it more in the first category, since Metabase should consider all the tables before making the determination as to whether or not to make the sum functions immediately available or not.
Thanks in advance for your consideration. I'm also submitting this as a reference in case someone else in the future is similarly left scratching their head before figuring it out. Unfortunately using the list of ISBN's as a joined table didn't limit the selection when using the sales file as the main file. It would have to be a filter - all 251 of them.
*** Note ***
The attempted workaround of creating custom expressions isn't working. I create the summed expressions, but they vanish if I go and add a filter or run the visualization. This on Metabase 0.46.1