config root man

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;
create table grandchild (
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)
on delete cascade on update restrict;
alter table grandchild add constraint fkname foreign key (a) references child
(a) on delete cascade on update restrict;
insert into parent values (1,1,1),(2,2,2);
insert into child values (1,1,1),(2,2,2);
insert into grandchild values (1,1,1),(2,2,2);
set ndb_deferred_constraints = 0;
begin;
delete from parent where a = 1;
select * from child order by 1,2,3;
a	b	c
2	2	2
select * from grandchild order by 1,2,3;
a	b	c
2	2	2
rollback;
set ndb_deferred_constraints = 1;
begin;
delete from parent where a = 1;
select * from child order by 1,2,3;
a	b	c
1	1	1
2	2	2
select * from grandchild order by 1,2,3;
a	b	c
1	1	1
2	2	2
commit;
set ndb_deferred_constraints = 0;
select * from child order by 1,2,3;
a	b	c
2	2	2
select * from grandchild order by 1,2,3;
a	b	c
2	2	2
drop table grandchild, child, parent;
create table t1 (
a int primary key,
b int null,
unique(b) using hash) engine = ndb;
Warnings:
Warning	1121	Ndb does not support unique index on NULL valued attributes, index access with NULL value will become full table scan
select max(a) into @maxa
from t1;
select min(a) into @mina
from t1;
select count(*) from t1;
count(*)
1025
select * from t1 p
where not exists (select 1 from t1 c where c.a = p.b);
a	b
0	NULL
alter table t1 add constraint fkname
foreign key (b) references t1 (a) on delete cascade on update restrict;
set ndb_deferred_constraints = 0;
begin;
update t1 set b = a + 1;
Got one of the listed errors
rollback;
set ndb_deferred_constraints = 1;
begin;
update t1 set b = a + 1;
commit;
ERROR 23000: Cannot add or update a child row: a foreign key constraint fails (Unknown error code)
begin;
update t1 set b = a + 1;
update t1 set b = null where a = @maxa;
commit;
select count(*) from t1;
count(*)
1025
select * from t1 p
where not exists (select 1 from t1 c where c.a = p.b);
a	b
1024	NULL
set ndb_deferred_constraints = 0;
begin;
delete from t1 where a = @maxa - 1;
select * from t1;
a	b
1024	NULL
rollback;
set ndb_deferred_constraints = 1;
begin;
delete from t1 where a = @maxa - 5;
select count(*) from t1;
count(*)
1024
commit;
select * from t1 order by 1,2;
a	b
1020	1021
1021	1022
1022	1023
1023	1024
1024	NULL
select * from t1 where b = @maxa;
a	b
1023	1024
select * from t1 where b = @maxa - 1;
a	b
1022	1023
select * from t1 where b = @maxa - 2;
a	b
1021	1022
select * from t1 where b = @maxa - 3;
a	b
1020	1021
drop table t1;