diff --git a/usql/row.h b/usql/row.h
index b4edf66..4ffb9cf 100644
--- a/usql/row.h
+++ b/usql/row.h
@@ -171,7 +171,7 @@ public:
 			case 5:
 				return (ColValue &) *std::get_if<ColBooleanValue>(&m_columns[i]);
 			default:
-				throw Exception("should not happen");
+				throw Exception("ColValue &operator[](int i), type index invalid :" + std::to_string(type_index));
 		}
 	}
 
diff --git a/usql/usql_dml.cpp b/usql/usql_dml.cpp
index eeca189..ed3dc6b 100644
--- a/usql/usql_dml.cpp
+++ b/usql/usql_dml.cpp
@@ -155,8 +155,7 @@ void USql::setup_order_columns(std::vector<ColOrderNode> &node, Table *table) {
 void USql::execute_distinct(SelectFromTableNode &node, Table *result) {
 	if (!node.distinct) return;
 
-	auto compare_rows = [](const Row &a, const Row &b) { return a.compare(b) >= 0; };
-	std::sort(result->m_rows.begin(), result->m_rows.end(), compare_rows);
+	std::sort(result->m_rows.begin(), result->m_rows.end(), [](const Row &a, const Row &b) { return a.compare(b) > 0; });
 
 	result->m_rows.erase(std::unique(result->m_rows.begin(), result->m_rows.end()), result->m_rows.end());
 }