diff --git a/sync/supported-sql.mdx b/sync/supported-sql.mdx
index 72b79abf..272a0233 100644
--- a/sync/supported-sql.mdx
+++ b/sync/supported-sql.mdx
@@ -270,6 +270,12 @@ Sync Streams support a subset of join syntax. The following rules define what is
 -- Valid: columns from one table
 SELECT comments.* FROM comments INNER JOIN issues ON comments.issue_id = issues.id
 
+-- Valid: multiple equality conditions (composite keys)
+SELECT comments.* FROM comments, issues
+  WHERE comments.issue_id = issues.id
+    AND comments.region = issues.region
+    AND issues.user_id = auth.user_id()
+
 -- Invalid: columns from multiple tables
 SELECT comments.*, issues.title FROM comments JOIN issues ON comments.issue_id = issues.id