Cannot add foreign key constraint on a simple code help please - mysql

Question

i am trying something apparently simple, but i just keep having the same error "Cannot add foreign key constraint", can anyone help me? I am using workbench with sql
drop table if exists table2;
create table if not exists table2(
id_kind int not null,
id_bod int not null,
id_doc int not null,
primary key (id_kind, id_bod, id_doc)
)engine=InnoDB default charset=latin1;
drop table if exists table1;
create table if not exists table1(
id_mov int not null,
id_kind int not null,
id_prod int,
id_bod int not null,
id_doc int not null,
primary key (id_mov),
key id_kind (id_kind),
key id_bod (id_bod),
key id_doc (id_doc),
foreign key table1 (id_kind) references table2 (id_kind),
foreign key table1 (id_bod) references table2 (id_bod),
foreign key table1 (id_doc) references table2 (id_doc)
)engine=InnoDB default charset=latin1;

Answer 1

I'm pretty sure you are trying to add the foreign key constraint to the wrong table.
Presumably table2 contains the kinds that are referenced by table1.
You'll have to reorder your code, id_kind should probably be the primary key for table2 and you need an index on id_kind in table1:
drop table if exists table2;
create table if not exists tabla2(
id_kind int not null,
primary key (id_kind)
)engine=InnoDB default charset=latin1;
drop table if exists table1;
create table if not exists table1(
id_mov int not null,
id_kind int not null,
id_prod int,
primary key (id_mov),
key id_kind (id_kind),
foreign key table1_ibfk_1 (id_kind) references table2 (id_kind)
)engine=InnoDB default charset=latin1;
UPDATE
It now looks like you want a composite foreign key, try this for your table1:
drop table if exists table1;
create table if not exists table1(
id_mov int not null,
id_kind int not null,
id_prod int,
id_bod int not null,
id_doc int not null,
primary key (id_mov),
key id_kind_id_bod_id_doc (id_kind, id_bod, id_doc),
foreign key table1_ibfk_1 (id_kind, id_boc, id_doc)
references table2 (id_kind, id_boc, id_doc),
)engine=InnoDB default charset=latin1;
I'm still not sure what each of these tables represent, or what you are trying to achieve.
You use the KEY (synonym for INDEX) line to set up an INDEX in your table that the FOREIGN KEY uses.
FOREIGN KEY docs