create table parent ( a int primary key auto_increment, b int not null, c int not null, unique(b) using hash, index(c)) engine = ndb; create table child ( a int primary key auto_increment, b int not null, c int not null, unique(b) using hash, index(c)) engine = ndb; alter table child add constraint fkname foreign key (a) references parent(a); insert into parent values (1,1,1); insert into child values (1,1,1); insert into child values (2,2,2); ERROR 23000: Cannot add or update a child row: a foreign key constraint fails (`test`.`child`, CONSTRAINT `fkname` FOREIGN KEY (`a`) REFERENCES `parent` (`a`) ON DELETE NO ACTION ON UPDATE NO ACTION) begin; delete from parent; delete from child; commit; begin; insert into child values (2,2,2); insert into parent values (2,2,2); commit; delete from child; delete from parent; insert into parent values (1,1,1); begin; insert into child values (1,1,1); begin; delete from parent; commit; commit; ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails (`test`.`child`, CONSTRAINT `fkname` FOREIGN KEY (`a`) REFERENCES `parent` (`a`) ON DELETE NO ACTION ON UPDATE NO ACTION) delete from child; delete from parent; alter table child drop foreign key fkname; alter table child add constraint fkname foreign key (b) references parent(a); insert into parent values (1,1,1); insert into child values (1,1,1); insert into child values (2,2,2); ERROR 23000: Cannot add or update a child row: a foreign key constraint fails (`test`.`child`, CONSTRAINT `fkname` FOREIGN KEY (`b`) REFERENCES `parent` (`a`) ON DELETE NO ACTION ON UPDATE NO ACTION) update child set b = 2 where a = 1; ERROR 23000: Cannot add or update a child row: a foreign key constraint fails (`test`.`child`, CONSTRAINT `fkname` FOREIGN KEY (`b`) REFERENCES `parent` (`a`) ON DELETE NO ACTION ON UPDATE NO ACTION) begin; delete from parent; delete from child; commit; begin; insert into child values (2,2,2); insert into parent values (2,2,2); commit; delete from child; delete from parent; insert into parent values (1,1,1); begin; insert into child values (1,1,1); begin; delete from parent; commit; commit; ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails (`test`.`child`, CONSTRAINT `fkname` FOREIGN KEY (`b`) REFERENCES `parent` (`a`) ON DELETE NO ACTION ON UPDATE NO ACTION) delete from child; delete from parent; alter table child drop foreign key fkname; alter table child add constraint fkname foreign key (a) references parent(b); insert into parent values (1,1,1); insert into child values (1,1,1); insert into child values (2,2,2); ERROR 23000: Cannot add or update a child row: a foreign key constraint fails (`test`.`child`, CONSTRAINT `fkname` FOREIGN KEY (`a`) REFERENCES `parent` (`b`) ON DELETE NO ACTION ON UPDATE NO ACTION) update parent set b = 2 where a = 1; ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails (`test`.`child`, CONSTRAINT `fkname` FOREIGN KEY (`a`) REFERENCES `parent` (`b`) ON DELETE NO ACTION ON UPDATE NO ACTION) begin; delete from parent; delete from child; commit; begin; insert into child values (2,2,2); insert into parent values (2,2,2); commit; delete from child; delete from parent; insert into parent values (1,1,1); begin; insert into child values (1,1,1); begin; delete from parent; commit; commit; ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails (`test`.`child`, CONSTRAINT `fkname` FOREIGN KEY (`a`) REFERENCES `parent` (`b`) ON DELETE NO ACTION ON UPDATE NO ACTION) delete from child; delete from parent; alter table child drop foreign key fkname; alter table child add constraint fkname foreign key (b) references parent(b); insert into parent values (1,1,1); insert into child values (1,1,1); update child set b = 2 where a = 1; ERROR 23000: Cannot add or update a child row: a foreign key constraint fails (`test`.`child`, CONSTRAINT `fkname` FOREIGN KEY (`b`) REFERENCES `parent` (`b`) ON DELETE NO ACTION ON UPDATE NO ACTION) insert into child values (2,2,2); ERROR 23000: Cannot add or update a child row: a foreign key constraint fails (`test`.`child`, CONSTRAINT `fkname` FOREIGN KEY (`b`) REFERENCES `parent` (`b`) ON DELETE NO ACTION ON UPDATE NO ACTION) update parent set b = 2 where a = 1; ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails (`test`.`child`, CONSTRAINT `fkname` FOREIGN KEY (`b`) REFERENCES `parent` (`b`) ON DELETE NO ACTION ON UPDATE NO ACTION) begin; delete from parent; delete from child; commit; begin; insert into child values (2,2,2); insert into parent values (2,2,2); commit; delete from child; delete from parent; insert into parent values (1,1,1); begin; insert into child values (1,1,1); begin; delete from parent; commit; commit; ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails (`test`.`child`, CONSTRAINT `fkname` FOREIGN KEY (`b`) REFERENCES `parent` (`b`) ON DELETE NO ACTION ON UPDATE NO ACTION) delete from child; delete from parent; alter table child drop foreign key fkname; alter table child add constraint fkname foreign key (c) references parent(a); insert into parent values (1,1,1); insert into child values (1,1,1); update child set c = 2 where a = 1; ERROR 23000: Cannot add or update a child row: a foreign key constraint fails (`test`.`child`, CONSTRAINT `fkname` FOREIGN KEY (`c`) REFERENCES `parent` (`a`) ON DELETE NO ACTION ON UPDATE NO ACTION) insert into child values (2,2,2); ERROR 23000: Cannot add or update a child row: a foreign key constraint fails (`test`.`child`, CONSTRAINT `fkname` FOREIGN KEY (`c`) REFERENCES `parent` (`a`) ON DELETE NO ACTION ON UPDATE NO ACTION) begin; delete from parent; delete from child; commit; begin; insert into child values (2,2,2); insert into parent values (2,2,2); commit; delete from child; delete from parent; insert into parent values (1,1,1); begin; insert into child values (1,1,1); begin; delete from parent; commit; commit; ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails (`test`.`child`, CONSTRAINT `fkname` FOREIGN KEY (`c`) REFERENCES `parent` (`a`) ON DELETE NO ACTION ON UPDATE NO ACTION) delete from child; delete from parent; alter table child drop foreign key fkname; alter table child add constraint fkname foreign key (c) references parent(b); insert into parent values (1,1,1); insert into child values (1,1,1); update child set c = 2 where a = 1; ERROR 23000: Cannot add or update a child row: a foreign key constraint fails (`test`.`child`, CONSTRAINT `fkname` FOREIGN KEY (`c`) REFERENCES `parent` (`b`) ON DELETE NO ACTION ON UPDATE NO ACTION) insert into child values (2,2,2); ERROR 23000: Cannot add or update a child row: a foreign key constraint fails (`test`.`child`, CONSTRAINT `fkname` FOREIGN KEY (`c`) REFERENCES `parent` (`b`) ON DELETE NO ACTION ON UPDATE NO ACTION) update parent set b = 2 where a = 1; ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails (`test`.`child`, CONSTRAINT `fkname` FOREIGN KEY (`c`) REFERENCES `parent` (`b`) ON DELETE NO ACTION ON UPDATE NO ACTION) begin; delete from parent; delete from child; commit; begin; insert into child values (2,2,2); insert into parent values (2,2,2); commit; delete from child; delete from parent; insert into parent values (1,1,1); begin; insert into child values (1,1,1); begin; delete from parent; commit; commit; ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails (`test`.`child`, CONSTRAINT `fkname` FOREIGN KEY (`c`) REFERENCES `parent` (`b`) ON DELETE NO ACTION ON UPDATE NO ACTION) delete from child; delete from parent; alter table child drop foreign key fkname; drop table parent, child;