Kevin Frank wrote a couple of great blog posts on the Summary List field type last year and ran into the problem with making a predicate relationship with a summary field–it can’t be done. He solved it last year by making a calculation field based on the summary field and making that field the predicate.
Now, with Dr. Ray Cologan’s guidance, he’s posted on a way to make that summary field a predicate relationship, and speed up the data processing, as well:
At the time I wrote, “Unfortunately we can’t use a summary field as a relational predicate, so let’s define a calculated field with a text result, to echo the summary list field.”
Well it turns out I was wrong. I happened to repeat the above remark to Dr. Ray Cologon the other day, and he astonished me by replying, “Actually, it is possible to use a summary field as a relational predicate,” and then left me to ponder how one might accomplish this.
Follow the link to see how he does this, and to download the help files. There’s also a part 2 with more example files.
via Summary List As Relational Predicate, part 1 | FileMakerHacks.