Merge Queries works like a lookup. For each row of the current query it finds the matching rows in a second query, on a key column such as Store. The matches arrive as a column of nested tables; expand it (the arrows in its header) and pick the columns you want.
The Join Kind decides which rows stay:
- Left Outer: every row of the first table, with matches from the second. The usual choice, like a lookup.
- Inner: only rows that match.
- Left Anti: only rows with no match. Handy to find what is missing.
Watch the key column of the second table. If a key appears twice there, every matching row comes back twice and your row count grows. The merge dialog tells you how many rows matched before you select OK.