create table counties (
county varchar(30) not null primary key,
country varchar(30)
) engine=ndb;
insert into counties values ('Berkshire','England'),('Shropshire','England'),
('Oxfordshire','England'),('Buckinghamshire','England'),('Somewhere','Earth');
create table towns (
town varchar(30) not null primary key,
county varchar(30) default "Somewhere",
index county_county_index (county),
constraint county_town foreign key (county)
references counties(county) on delete set default on update restrict
) engine=ndb;
insert into towns values ('Maidenhead','Berkshire'),('Reading','Berkshire'),
('Shrewsbury','Shropshire'),('Oxford','Oxfordshire');
delete from counties where county='Shropshire';
ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails (`test`.`towns`, CONSTRAINT `county_town` FOREIGN KEY (`county`) REFERENCES `counties` (`county`) ON DELETE SET DEFAULT ON UPDATE RESTRICT)
show warnings;
Level	Code	Message
Warning	1296	Got error 256 'Foreign key constraint violated: Referenced row exists' from NDB
Error	1451	Cannot delete or update a parent row: a foreign key constraint fails (`test`.`towns`, CONSTRAINT `county_town` FOREIGN KEY (`county`) REFERENCES `counties` (`county`) ON DELETE SET DEFAULT ON UPDATE RESTRICT)
drop table towns, counties;