I have no idea how feasible this query is, so please bear with me.
There are three tables I need to query against: call them Table1, Table2 and
Table1 has a column named "PartNumber", while Table2 has one named
"MachineNumber". Table12 contains both "PartNumber" and "MachineNumber"
columns. Think of Table12 as the "official" guide as to which MachineNumber
a given PartNumber belongs to. I'll show below that the guide has been
ignored sometimes, and I have to figure out how widespread the problem is.
Table2 and Table1 have a parent-child relationship, where one entry in
Table2 can ...