Is 'AS' creating a temporary alias or a true new column?

Question

For exemple with the folowing code :

SELECT CONCAT(FirstName,', ', City) AS new_column FROM customers;

Will the column "new_column" be created or is it a kind of alias which disappear at the end of the request?

Answer 1

Correction: it is ALTER TABLE and so on.

Answer 2

AS is temporary. For a new column use
ALTER tablename ADD columnname type.

Answer 3

Oh yeah, thanks!