question about ANY data type

[Wes Peng]

what does ANY data type mean?

apache drill (dfs.pyh)> desc foodmart;
+-----------------+-----------+-------------+
|   COLUMN_NAME   | DATA_TYPE | IS_NULLABLE |
+-----------------+-----------+-------------+
| employee_id     | ANY       | YES         |
| full_name       | ANY       | YES         |
| position_title  | ANY       | YES         |
| birth_date      | ANY       | YES         |
| salary          | ANY       | YES         |
| education_level | ANY       | YES         |
+-----------------+-----------+-------------+
6 rows selected (0.534 seconds)

I saw this type can be used in aggregate functions. doesn't it need a 
cast() translation?

apache drill (dfs.pyh)> select avg(salary) as avgsal from foodmart;
+--------------------+
|       avgsal       |
+--------------------+
| 4019.6017316017314 |
+--------------------+
1 row selected (0.452 seconds)


Thanks