Re: FOEIGN KEY

[Victoria Reznichenko]

"Mulugeta Maru" <mulugetamaru@stripped> wrote:
> Can a field in one table be a foreign key of another table's field which is 
> also a foreign key of a third table?
> 

Sure.
For example:

mysql> CREATE TABLE t1 (
    ->   id int NOT NULL default '0',
    ->   PRIMARY KEY  (id)
    -> ) TYPE=InnoDB;
Query OK, 0 rows affected (0.00 sec)

mysql> CREATE TABLE t2 (
    ->   id int NOT NULL default '0',
    ->   pid int default NULL,
    ->   PRIMARY KEY  (id),
    ->   KEY (pid),
    ->   FOREIGN KEY (pid) REFERENCES t1 (id)
    -> ) TYPE=InnoDB;
Query OK, 0 rows affected (0.00 sec)

mysql> CREATE TABLE t3 (
    ->   id int NOT NULL default '0',
    ->   pid int default NULL,
    ->   PRIMARY KEY  (id),
    ->   KEY (pid),
    ->   FOREIGN KEY (pid) REFERENCES t2 (pid)
    -> ) TYPE=InnoDB;
Query OK, 0 rows affected (0.00 sec)



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