mysql> set sql_mode='';
Query OK, 0 rows affected (0.00 sec)

mysql>
mysql> drop table if exists t,s;
Query OK, 0 rows affected (0.01 sec)

mysql> drop view if exists t,s;
Query OK, 0 rows affected, 2 warnings (0.00 sec)

mysql> create table t (a int primary key) engine=innodb ;
Query OK, 0 rows affected (0.01 sec)

mysql> insert into t values(1),(2),(3),(4);
Query OK, 4 rows affected (0.00 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> analyze table t;
+--------+---------+----------+----------+
| Table  | Op      | Msg_type | Msg_text |
+--------+---------+----------+----------+
| test.t | analyze | status   | OK       |
+--------+---------+----------+----------+
1 row in set (0.00 sec)

mysql>
mysql> create table s(b int auto_increment primary key,c int,d int,key(c))engine=innodb;
Query OK, 0 rows affected (0.01 sec)

mysql> insert into s(c) values(1),(2),(3),(4);
Query OK, 4 rows affected (0.00 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> analyze table s;
+--------+---------+----------+----------+
| Table  | Op      | Msg_type | Msg_text |
+--------+---------+----------+----------+
| test.s | analyze | status   | OK       |
+--------+---------+----------+----------+
1 row in set (0.00 sec)

mysql>
mysql> select a,d from t left join s on c=a;
+---+------+
| a | d    |
+---+------+
| 1 | NULL |
| 2 | NULL |
| 3 | NULL |
| 4 | NULL |
+---+------+
4 rows in set (0.00 sec)

mysql> select a,group_concat(d)q from t left join s on c=a;
+---+------+
| a | q    |
+---+------+
| 1 | NULL |
+---+------+
1 row in set (0.00 sec)

mysql> select a,group_concat(d)q from t left join s on c=a group by a;
+---+------+
| a | q    |
+---+------+
| 1 | NULL |
| 2 | NULL |
| 3 | NULL |
| 4 | NULL |
+---+------+
4 rows in set (0.00 sec)

mysql>
mysql> set sql_mode='only_full_group_by';
Query OK, 0 rows affected (0.00 sec)

mysql>
mysql> select a,d from t left join s on c=a;
+---+------+
| a | d    |
+---+------+
| 1 | NULL |
| 2 | NULL |
| 3 | NULL |
| 4 | NULL |
+---+------+
4 rows in set (0.00 sec)

mysql> select a,group_concat(d)q from t left join s on c=a;
ERROR 1140 (42000): Mixing of GROUP columns (MIN(),MAX(),COUNT(),...) with no GROUP columns is illegal if there is no GROUP BY clause
mysql> select a,group_concat(d)q from t left join s on c=a group by a;
+---+------+
| a | q    |
+---+------+
| 1 | NULL |
| 2 | NULL |
| 3 | NULL |
| 4 | NULL |
+---+------+
4 rows in set (0.00 sec)

mysql>
mysql> select version();
+------------------+
| version()        |
+------------------+
| 5.0.96-community |
+------------------+
1 row in set (0.00 sec)

mysql>