Added a test case for bug #20293 "group by cuts off value from time_format"

mysql-test/r/func_time.result

@@ -1207,3 +1207,7 @@ SET NAMES DEFAULT;
 select str_to_date('10:00 PM', '%h:%i %p') + INTERVAL 10 MINUTE;
 str_to_date('10:00 PM', '%h:%i %p') + INTERVAL 10 MINUTE
 NULL
+SELECT TIME_FORMAT(SEC_TO_TIME(a),"%H:%i:%s") FROM (SELECT 3020399 AS a UNION SELECT 3020398 ) x GROUP BY 1;
+TIME_FORMAT(SEC_TO_TIME(a),"%H:%i:%s")
+838:59:58
+838:59:59

mysql-test/t/func_time.test

@@ -713,3 +713,11 @@ SET NAMES DEFAULT;
 #
 
 select str_to_date('10:00 PM', '%h:%i %p') + INTERVAL 10 MINUTE;
+
+
+#
+# Bug #20293: group by cuts off value from time_format
+#
+# Check if using GROUP BY with TIME_FORMAT() produces correct results
+
+SELECT TIME_FORMAT(SEC_TO_TIME(a),"%H:%i:%s") FROM (SELECT 3020399 AS a UNION SELECT 3020398 ) x GROUP BY 1;