MySQL ORDER BY with EXPLAIN command

Let us first create a table −

mysql> create table DemoTable606 (Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,FirstName varchar(100)); Query OK, 0 rows affected (0.56 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable606(FirstName) values('John'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable606(FirstName) values('Robert'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable606(FirstName) values('Chris'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable606(FirstName) values('David'); Query OK, 1 row affected (0.13 sec)

Display all records from the table using select statement −

mysql> select *from DemoTable606;

This will produce the following output −

+----+-----------+ | Id | FirstName | +----+-----------+ |  1 | John      | |  2 | Robert    | |  3 | Chris     | |  4 | David     | +----+-----------+ 4 rows in set (0.00 sec)

Following is the query to work with EXPLAIN command::

mysql> explain select * from DemoTable606 order by Id; +----+-------------+--------------+------------+-------+---------------+---------+---------+------+------+----------+-------+ | id | select_type | table        | partitions | type  | possible_keys | key     | key_len | ref  | rows | filtered | Extra | +----+-------------+--------------+------------+-------+---------------+---------+---------+------+------+----------+-------+ | 1  | SIMPLE      | DemoTable606 | NULL       | index | NULL          | PRIMARY | 4       | NULL | 4    | 100.00   | NULL  | +----+-------------+--------------+------------+-------+---------------+---------+---------+------+------+----------+-------+ 1 row in set, 1 warning (0.00 sec) mysql> explain select * from DemoTable606 order by Id,FirstName; +----+-------------+--------------+------------+------+---------------+------+---------+------+------+----------+----------------+ | id | select_type | table        | partitions | type | possible_keys | key  | key_len | ref  | rows | filtered | Extra          | +----+-------------+--------------+------------+------+---------------+------+---------+------+------+----------+----------------+ | 1  | SIMPLE      | DemoTable606 | NULL       | ALL  | NULL          | NULL | NULL    | NULL | 4    | 100.00   | Using filesort | +----+-------------+--------------+------------+------+---------------+------+---------+------+------+----------+----------------+ 1 row in set, 1 warning (0.00 sec) mysql> explain select * from DemoTable606 order by Id,RAND(); +----+-------------+--------------+------------+------+---------------+------+---------+------+------+----------+---------------------------------+ | id | select_type | table        | partitions | type | possible_keys | key  | key_len | ref  | rows | filtered | Extra | +----+-------------+--------------+------------+------+---------------+------+---------+------+------+----------+---------------------------------+ | 1 | SIMPLE | DemoTable606 | NULL | ALL | NULL | NULL | NULL | NULL | 4 | 100.00 | Using temporary; Using filesort | +----+-------------+--------------+------------+------+---------------+------+---------+------+------+----------+---------------------------------+ 1 row in set, 1 warning (0.00 sec)