MySQL query to order timestamp in descending order but place the timestamp 0000-00-00 00:00:00 first?

Let us first create a table &mnus;

mysql> create table DemoTable
(
   `timestamp` timestamp
);
Query OK, 0 rows affected (1.12 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable values(now());
Query OK, 1 row affected (0.27 sec)
mysql> insert into DemoTable values('00:00:00');
Query OK, 1 row affected (0.73 sec)
mysql> insert into DemoTable values('2018-01-10 12:34:45');
Query OK, 1 row affected (0.80 sec)
mysql> insert into DemoTable values('2019-12-31 10:50:45');
Query OK, 1 row affected (0.84 sec)

Display all records from the table using select statement −

mysql> select *from DemoTable;

This will produce the following output −

+---------------------+
| timestamp           |
+---------------------+
| 2019-08-17 06:17:12 |
| 0000-00-00 00:00:00 |
| 2018-01-10 12:34:45 |
| 2019-12-31 10:50:45 |
+---------------------+
4 rows in set (0.00 sec)

Following is the query to order the timestamp in descending order by first displaying the 0 timestamp −

mysql> select *from DemoTable order by (`timestamp`=0) DESC,`timestamp` DESC;

This will produce the following output −

+---------------------+
| timestamp           |
+---------------------+
| 0000-00-00 00:00:00 |
| 2019-12-31 10:50:45 |
| 2019-08-17 06:17:12 |
| 2018-01-10 12:34:45 |
+---------------------+
4 rows in set (0.00 sec)