Looking at the docs:

http://dev.mysql.com/doc/refman/5.6/en/create-table-foreign-keys.html

how do I alter the child table, links, so that it has a foreign key with
the parent table, feeds?

The feed_id field in links should, in fact, be constrained by the foreign
key of feeds with a RESTRICT reference option.



mysql>
mysql> show tables;
+---------------------------+
| Tables_in_rome_aggregator |
+---------------------------+
| feeds |
| links |
| pages |
+---------------------------+
3 rows in set (0.00 sec)

mysql>
mysql> describe feeds;
+----------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| created | datetime | NO | | NULL | |
| accessed | varchar(45) | NO | | NULL | |
| url | varchar(767) | NO | UNI | NULL | |
| status | int(11) | NO | | 0 | |
+----------+--------------+------+-----+---------+----------------+
5 rows in set (0.05 sec)

mysql>
mysql> describe links;
+---------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| created | datetime | NO | | NULL | |
| feed_id | int(11) | NO | | 0 | |
| link | varchar(767) | NO | UNI | NULL | |
| status | int(11) | NO | | 0 | |
+---------+--------------+------+-----+---------+----------------+
5 rows in set (0.00 sec)

mysql>


While I know that I should alter the table, I don't know the syntax to
establish the foreign key constraint.


thanks,

Thufir


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