MySQL ON vs USING?

In general, we use ON in MySQL. In Joins, we use ON in a set of columns. USING is useful when both the tables share a column of the exact same name on which they join.

Example of On.

Creating our first table.

mysql> CREATE table ForeignTableDemo
   -> (
   -> Id int,
   -> Name varchar(100),
   - > FK int
   - > );
Query OK, 0 rows affected (0.47 sec)

Creating our second table.

mysql> CREATE table PrimaryTableDemo
   - > (
   - >  FK int,
   - > Address varchar(100),
   - > primary key(FK)
   - > );
Query OK, 0 rows affected (0.47 sec)

Let us now add constraints.

mysql> ALTER table ForeignTableDemo add constraint FKConst foreign key(FK) references PrimaryTableDemo(FK);
Query OK, 0 rows affected (1.54 sec)
Records: 0  Duplicates: 0  Warnings: 0

To add records into the second table.

mysql> INSERT into PrimaryTableDemo values(1,'US');
Query OK, 1 row affected (0.10 sec)

mysql> INSERT into PrimaryTableDemo values(2,'UK');
Query OK, 1 row affected (0.14 sec)

mysql>  INSERT into PrimaryTableDemo values(3,'Unknown');
Query OK, 1 row affected (0.08 sec)

Displaying all the records.

mysql> SELECT * from PrimaryTableDemo;

The following is the output.

+----+---------+
| FK | Address |
+----+---------+
|  1 | US      |
|  2 | UK      |
|  3 | Unknown |
+----+---------+
3 rows in set (0.00 sec)

Now, to add records into the first table.

mysql>  INSERT into ForeignTableDemo values (1,'John',1);
Query OK, 1 row affected (0.20 sec)

mysql>  INSERT into ForeignTableDemo values (2,'Bob',2);
Query OK, 1 row affected (0.27 sec)

Let us now display all the records from the first table.

mysql> SELECT * from ForeignTableDemo;

Here is the output.

+------+------+------+
| Id   | Name | FK   |
+------+------+------+
|    1 | John |    1 |
|    2 | Bob  |    2 |
+------+------+------+
2 rows in set (0.00 sec)

The query for straight join that displays only matching rows is shown below. We have used ON here.

mysql> SELECT ForeignTableDemo.Id, ForeignTableDemo.Name, PrimaryTableDemo.Address
   - > from ForeignTableDemo
   - > join PrimaryTableDemo
   - > on ForeignTableDemo.FK = PrimaryTableDemo.FK;

The following is the output.

+------+------+---------+
| Id   | Name | Address |
+------+------+---------+
|    1 | John | US      |
|    2 | Bob  | UK      |
+------+------+---------+
2 rows in set (0.14 sec)

Example of USING.

The following is the syntax of USING in MySQL, that displays the record where FK = 1.

mysql> select *from ForeignTableDemo join PrimaryTableDemo using(FK) where FK=1;

Here is the output.

+------+------+------+---------+
| FK   | Id   | Name | Address |
+------+------+------+---------+
|    1 |    1 | John | US      |
+------+------+------+---------+
1 row in set (0.09 sec)