Found Set Awareness Revisited
Finding more ways to do ‘Finds’ on a found set of data.
Now that’s a mouthful.
Kevin Frank explores ways to refine found sets quickly and easily without having FileMaker query the entire database each time. That may sound mundane, but in large datasets, refining found sets is much faster than starting over. The other benefit? Keeping the found set active while finding and reporting information within that found set. And there are problems with doing these things in FileMaker:
The SQL Found Set Issue In A Nutshell
The concept of a “found set” does not exist in FM/SQL, so when you perform a SQL query in FileMaker, the query ignores your current found set. Fortunately, FM/SQL can be tricked into querying only the records within the current found set, by using a SQL “IN” clause, and feeding that IN clause a comma-delimited set of primary keys corresponding to the records in the found set.
Frank provides three different ways to solve this problem, two using SQL and one that is purely FileMaker. And he provides an downloadable example file with custom functions, as well, at the link. Well worth the read.
Source: Found Set Awareness Revisited | FileMakerHacks