SELECT into SELECT

Lets explain the syntax with an example. The input data is:

mysql> describe employee;
+--------------+-------------+------+-----+---------+-------+ 
| Field        | Type        | Null | Key | Default | Extra |
+--------------+-------------+------+-----+---------+-------+ 
| LastName     | varchar(25) | YES  | UNI | NULL    |       | 
| DepartmentID | int(4)      | YES  |     | NULL    |       |
+--------------+-------------+------+-----+---------+-------+ 

2 rows in set (0.00 sec)

mysql> select * from employee;
+-----------+--------------+
| LastName  | DepartmentID |
+-----------+--------------+
| Rafferty  |           31 |
| Jones     |           33 |
| Steinberg |           33 |
| Robinson  |           34 |
| Smith     |           34 |
| John      |         NULL |
+-----------+--------------+
6 rows in set (0.01 sec)

mysql> select t1.* from (SELECT * FROM employee WHERE DepartmentID > 32) AS t1 WHERE t1.DepartmentID < 34; 
+-----------+--------------+
| LastName  | DepartmentID |
+-----------+--------------+
| Jones     |           33 |
| Steinberg |           33 |
+-----------+--------------+
2 rows in set (0.00 sec)

Note: If inner table (generated by the inner select) has no alias, this error is returned:

mysql> select * from (SELECT * FROM employee WHERE DepartmentID > 32); 

ERROR 1248 (42000): Every derived table must have its own alias