DOCSP-15757 Note that SQL in ADL is read-only (#149)

kanchana-mongodb · web-flow · commit f712e506de56 · 2021-04-30T12:41:05.000-07:00
* DOCSP-15757 Note that SQL in ADL is read-only * DOCSP-15757 updates for feedback
diff --git a/source/reference/pipeline/sql.txt b/source/reference/pipeline/sql.txt
@@ -14,8 +14,13 @@
 
 .. include:: /includes/extracts/fact-sql-beta-message.rst
 
-``$sql`` processes a SQL query of the data in a collection. 
-It must be the first stage in the pipeline.  
+``$sql`` processes an SQL query of the data in a collection. The 
+``$sql`` stage: 
+
+- Must be the first stage in the pipeline.  
+- Supports ``SELECT`` and ``UNION`` statements only.
+
+Use this stage for read-only queries.
 
 .. _adl-sql-syntax:
 
