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Re: Help in MySQL
Posted by: Roland Bouman
Date: August 12, 2005 11:56AM

I recommend you read this part of the manual:

but here's a quick start

create table a (
id int unsigned not null primary key
, ...any other columns
) engine = InnoDB

create table b (
ref_a int unsigned
) engine = InnoDB

alter table b
add constraint fk_b_a
foreign key (
) references a (
on delete cascade

1) both referenced and referencing tables need to be InnoDB tables
2) the referenced table needs to have a primary key or unique constraint
3) the referencing table need to have columns that can refer to the columns in the referenced table's primary key or unique constraint. The datatypes of these columns should be identical, but they need nod have the same name.
4) you have to create a foreign key constraint on the referencing table.

The tables can be in different databases, but only as long as these reside in the same MySQL server instance. If your tables are not innodb tables, the synta is parsed but not enforced, so beware of that.

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Written By
August 11, 2005 10:38PM
Re: Help in MySQL
August 12, 2005 11:56AM

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