When users have problems with query layers, 9 times out of 10, the issue is with the Unique ID field. There are usually duplicates in that field that the user was unaware of.
It would be great to have a button in the query layer Contents properties that checks for duplicates in the Unique ID column in the underlying data (using the raw SQL query).
Not to be confused with checking for duplicates in the attribute table/feature layer (idea: Select By Attributes — Select Duplicates), which is not a true representation of the underlying data. If there are duplicates in the Unique ID field, then the duplicate rows will likely be silently/automatically omitted from the attribute table/feature layer, so checking for dups in the attribute table/feature layer wouldn't help us. We need to check for dups in the underlying data.
Could a "Check for Duplicate IDs" button be added to the query layer properties?
