should be it

external/duckdb/test/sql/aggregate/distinct/issue2656.test

@@ -0,0 +1,43 @@
+# name: test/sql/aggregate/distinct/issue2656.test
+# description: Issue #2656: DISTINCT + ORDER produces incorrect result
+# group: [distinct]
+
+statement ok
+PRAGMA enable_verification
+
+statement ok
+CREATE TABLE T (t1 int, t2 int);
+
+statement ok
+INSERT INTO t VALUES (1, 1), (1, 2);
+
+query I
+SELECT DISTINCT t1
+FROM T
+ORDER BY t1, t2;
+----
+1
+
+query II
+SELECT DISTINCT ON (1) t1, t2
+FROM T
+ORDER BY t1, t2;
+----
+1	1
+
+query I
+SELECT DISTINCT t1 FROM T
+UNION
+SELECT DISTINCT t1 FROM T
+ORDER BY t1;
+----
+1
+
+query I
+SELECT DISTINCT t1 FROM T
+UNION ALL
+SELECT DISTINCT t1 FROM T
+ORDER BY t1;
+----
+1
+1