docs: blurb about msq union all (apache#15223)

(cherry picked from commit 8769541)
317brian · Oct 31, 2023 · f7cc075 · f7cc075
1 parent d3fad8f
commit f7cc075
Showing 1 changed file with 1 addition and 3 deletions.
diff --git a/docs/querying/sql.md b/docs/querying/sql.md
@@ -224,9 +224,7 @@ UNION ALL
 SELECT COUNT(*) FROM tbl WHERE my_column = 'value2'
 ```
 
-:::info
- With top-level queries, you can't apply GROUP BY, ORDER BY, or any other operator to the results of a UNION ALL.
-:::
+Certain limitations apply when you use a top-level UNION ALL. For all top-level UNION ALL queries, you can't apply a GROUP BY, ORDER BY, or any other operator to the results of the query. For any top-level UNION ALL that uses the MSQ task engine, the SQL planner attempts to plan the top-level UNION ALL as a table-level UNION ALL. Because of this, UNION ALL queries that use the MSQ task engine always behave the same as table-level UNION ALL queries. They have the same characteristics and limitations. If the planner can't plan the query as a table-level UNION ALL, the query fails.
 
 ### Table-level