Is it possible to see the result of left join of two tables?

[colap]

http://www.sitepoint.com/understanding-sql-joins-mysql-database/

 

Is it possible to see the result of left join of two tables(without on clause)?

mysql> select * from user;
+----+----------+--------+
| id | name     | course |
+----+----------+--------+
|  1 | Alice    |      1 |
|  2 | Bob      |      1 |
|  3 | Caroline |      2 |
|  4 | David    |      5 |
|  5 | Emma     |   NULL |
+----+----------+--------+
5 rows in set (0.00 sec)

mysql> select * from course;
+----+------------+
| id | name       |
+----+------------+
|  1 | HTML5      |
|  2 | CSS3       |
|  3 | Javascript |
|  4 | PHP        |
|  5 | MySQL      |
+----+------------+
5 rows in set (0.00 sec)

mysql> SELECT * FROM `user` left join course on user.course=course.id;
+----+----------+--------+------+-------+
| id | name     | course | id   | name  |
+----+----------+--------+------+-------+
|  1 | Alice    |      1 |    1 | HTML5 |
|  2 | Bob      |      1 |    1 | HTML5 |
|  3 | Caroline |      2 |    2 | CSS3  |
|  4 | David    |      5 |    5 | MySQL |
|  5 | Emma     |   NULL | NULL | NULL  |
+----+----------+--------+------+-------+
5 rows in set (0.00 sec)

Why/how is id=NULL and name=NULL for Emma,NULL?

Edited August 21, 2015 by php-coder

[Barand]

Because there is no record in course table where the course.id matches the user.course for Emma in the user table

Edited August 21, 2015 by Barand

[Psycho]

What do you mean by "Is it possible to see the result of left join of two tables(without on clause)?"

 

What do you expect to get without an ON clause for a LEFT/RIGHT JOIN? Why don't you explain what you are trying to achieve?