Опитайте да промените харесванията на...
count(select * from bookings where b.id_customer = c.id)
...до...
(select count(*) from bookings where b.id_customer = c.id)
Опитайте да промените харесванията на...
count(select * from bookings where b.id_customer = c.id)
...до...
(select count(*) from bookings where b.id_customer = c.id)