How does the MySQL GROUP BY clause behave like a DISTINCT clause?

When we use GROUP BY clause in SELECT statement without using aggregate function, it behaves like DISTINCT clause. For example, we have the following table -

mysql> Select * from testing;
+------+---------+---------+
| id   | fname   | Lname   |
+------+---------+---------+
|  200 | Raman   | Kumar   |
|  201 | Sahil   | Bhalla  |
|  202 | Gaurav  | NULL    |
|  203 | Aarav   | NULL    |
|  204 | Harshit | Khurana |
|  205 | Rahul   | NULL    |
|  206 | Piyush  | Kohli   |
|  207 | Lovkesh | NULL    |
|  208 | Gaurav  | Kumar   |
|  209 | Raman  | Kumar    |
+------+---------+---------+
10 rows in set (0.00 sec)

By using the DISTINCT clause on the "Lname" column, MySQL returns the following result set.

mysql> select Distinct LNAME from testing;
+---------+
| LNAME   |
+---------+
| Kumar   |
| Bhalla  |
| NULL    |
| Khurana |
| Kohli   |
+---------+
5 rows in set (0.00 sec)

Now, by using the GROUP BY clause as shown below, we can get the same result set as that obtained using DISTINCT -

mysql> Select LNAME from testing GROUP BY Lname;
+---------+
| LNAME   |
+---------+
| NULL    |
| Bhalla  |
| Khurana |
| Kohli   |
| Kumar   |
+---------+
5 rows in set (0.04 sec)

We can observe the results returned by MySQL There is a difference between the sets, a MySQL query using the GROUP BY clause returns a result set that is sorted, while a MySQL query using the DISTINCT clause returns an unsorted result set. p>

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