title: Table measuring using other table
body: <p>I have two tables in a DB. The tables have an ID column.  One table is always accurate (Table Always) and the other table is sometimes accurate (Table Sometimes). Table Sometimes could have multiple IDs mapping to a single ID on Table Always. Ideally, I want to have a 1-1 mapping between the two tables, but that is not case. How can I come up with an approach to measure Table Sometimes hit/accuracy based on a successful mapping (1 - 1) to Table Always</p>