drop table xx_kniha;
drop table xx_autor;
drop table xx_jazyk;
drop table xx_oddelenie;
drop table xx_mesto;
drop table xx_kategoria;
drop table xx_citatel;
drop table xx_vyprez;
drop table xx_vrknihy;

alter table xx_kniha drop foreign key id_autor;
alter table xx_kniha drop foreign key id_jazyk;
alter table xx_kniha drop foreign key id_oddelenie;
alter table xx_citatel drop foreign key id_mesto;
alter table xx_citatel drop foreign key id_kategoria;
alter table xx_vyprez drop foreign key id_citatel;
alter table xx_vrKnihy drop foreign key id_vyprez;
alter table xx_vrKnihy drop foreign key id_vrkniha;