How can I describe all tables in the database through one statement?

There is no statement that describe all tables at once. But you may want to do something like this :

SELECT * FROM information_schema.columns WHERE table_schema = 'db_name';

because the other suggestions made very much mess on the screen or just did not do the trick here is a hack for a small db:

describe table_a; describe table_b; describe table_c; 

and so on