Adding a column to a Union subquery, causes the main query diagram to lose checked columns and relationship lines
A query was created and saved using Query Builder which had a main query and a UNION (U) subquery.
The query is then re-opened to add a column to the main query diagram and then adding the same column to the Union subquery diagram. On going back to the main query diagram, the relationship line is missing and the columns are all unchecked in the 'subquery' box.
Manually add back the relationship and columns checked to the subquery
Waiting for fix in a future release of Toad Data Point