Preserve aggregated attributes of singleton groups

scripts-available/CDB_Overviews.sql

@@ -304,8 +304,9 @@ BEGIN
     --     'A', 'B', 'A', 'C', 'D' => 'A/B/C/...'
     -- Other ideas: if value is unique then use it, otherwise use something
     -- like '*' or '(varies)' or '(multiple values)', or NULL
-    RETURN '''''::' || column_type;
-  ELSE RETURN 'NULL::' || column_type;
+    RETURN 'CASE count(*) WHEN 1 THEN string_agg(' || qualified_column || ',''/'') ELSE ''*''' || ' END::' || column_type;
+  ELSE
+    RETURN 'CASE count(*) WHEN 1 THEN MIN(' || qualified_column || ') ELSE NULL END::' || column_type;
   END CASE;
 END
 $$ LANGUAGE PLPGSQL IMMUTABLE;