every derived yable must have its own alias

1
2/*Every derived table (AKA sub-query) must indeed have an alias. 
3I.e. each query in brackets must be given an alias (AS whatever), 
4which can the be used to refer to it in the rest of the outer query.
5*/
6SELECT ID FROM (
7    SELECT ID, msisdn FROM (
8        SELECT * FROM TT2
9    ) AS T
10) AS T
11