A word of warning around merge queries that we’ve just discovered, but is not made clear in the documentation:
When two queries are merged, the first 5000 rows are taken from each query and merged, regardless of what row limits you set in each query individually. So if you have a queries with potential results larger than 5000 rows, merge queries are not advised.
For example, if you were looking to merge a query of customer ID and order count, with a query of customer ID and complaint count, if your top ordering customer was the 5001th most frequent complainer, you would just see null for complaint count.
As such merge queries should be used with extreme caution with larger datasets to avoid misleading results