What is the error "Every derived table must have its own alias" in MySQL?

Question

I am running this query on MySQL

SELECT ID FROM (     SELECT ID, msisdn     FROM (         SELECT * FROM TT2     ) ); 

and it is giving this error:

Every derived table must have its own alias.

What's causing this error?

Answer 1

Every derived table (AKA sub-query) must indeed have an alias. I.e. each query in brackets must be given an alias (AS whatever), which can the be used to refer to it in the rest of the outer query.

SELECT ID FROM (     SELECT ID, msisdn FROM (         SELECT * FROM TT2     ) AS T ) AS T 

In your case, of course, the entire query could be replaced with:

SELECT ID FROM TT2 

Answer 2

I think it's asking you to do this:

SELECT ID FROM (SELECT ID,              msisdn        FROM (SELECT * FROM TT2) as myalias      ) as anotheralias; 

But why would you write this query in the first place?