mysql> create table t1 ( i int, j int);
Query OK, 0 rows affected (0.06 sec)

mysql> create table t2 ( i int, j int);
Query OK, 0 rows affected (0.06 sec)

mysql> insert into t1 values (1,1),(2,2),(2,3),(3,9);
Query OK, 4 rows affected (0.02 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> insert into t2 values (1,10),(1,11),(2,20),(10,10);
Query OK, 4 rows affected (0.02 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> select * from t1 left join t2 on t1.i=t2.i;
+------+------+------+------+
| i    | j    | i    | j    |
+------+------+------+------+
|    1 |    1 |    1 |   10 |
|    1 |    1 |    1 |   11 |
|    2 |    2 |    2 |   20 |
|    2 |    3 |    2 |   20 |
|    3 |    9 | NULL | NULL |
+------+------+------+------+
5 rows in set (0.00 sec)


mysql> select * from t1 inner join t2 on t1.i=t2.i;
+------+------+------+------+
| i    | j    | i    | j    |
+------+------+------+------+
|    1 |    1 |    1 |   10 |
|    1 |    1 |    1 |   11 |
|    2 |    2 |    2 |   20 |
|    2 |    3 |    2 |   20 |
+------+------+------+------+
4 rows in set (0.00 sec)

mysql> select * from t1 right join t2 on t1.i=t2.i;
+------+------+------+------+
| i    | j    | i    | j    |
+------+------+------+------+
|    1 |    1 |    1 |   10 |
|    1 |    1 |    1 |   11 |
|    2 |    2 |    2 |   20 |
|    2 |    3 |    2 |   20 |
| NULL | NULL |   10 |   10 |
+------+------+------+------+
5 rows in set (0.00 sec)