Tagged Questions

A type of integrity constraint used in a RDBMS platform to ensure that a value in a column matches one of a range of key values from another table.

learn more… | top users | synonyms

4
votes
2answers
812 views

Using IDs from multiple tables in a single column

One of my co-workers created a schema similar to the following. This is a simplified schema including only the parts necessary to address this question. The system rules are as follows: ...
2
votes
1answer
137 views

InnoDB foreign key and index duplication?

I'm have a part table like this: part_id INT manufacturer_id INT supplier_id INT part_number VARCHAR(50) part_description VARCHAR(120) with foreign ...
0
votes
1answer
137 views

Derived value not calculating as expected using combination of FK and Triggers (MySQL)

I'm having trouble with calculating a derived value using a combination of triggers and foreign key constraints. There are 3 tables involved in this arrangement responses ------------------------ ...
0
votes
2answers
1k views

Query PostgreSQL 9.0 table on foreign key value?

Noob-type question: Say I have two tables, candies and colors. The colors table holds just code/value pairs like 01 yellow, 02 blue, 03 green, etc. and is referenced in the candies table by code. ...
6
votes
2answers
3k views

Non-unique multicolumn foreign key

I have a "comments" table that models a conversation on a topic, like this: id serial topic_id integer parent_comment_id integer body text So, every comment has a reference to its topic AND ...
2
votes
1answer
578 views

Question on Design for User + User Groups + User Types + Subscriptions Model

I am redeveloping an existing web application with both weak source code and a weak underlying database design. I'm trying to develop things in a way that future expansion will be much easier, ...
3
votes
1answer
874 views

Foreign Key violation - not sure why

I have the following two tables with a foreign key on status_id: mysql> describe usr_cookbook; +-----------+-----------+------+-----+-------------------+-------+ | Field | Type | Null | ...
10
votes
3answers
199 views

Are there any database engines which will intuit the join condition based on the existing foreign keys?

It seems strange to me that, when I've defined a foreign key, the engine cannot use this information to automatically figure out the correct JOIN expressions, but instead requires me to re-type the ...
6
votes
3answers
259 views

What does the output of a JOIN statement look like?

I've been wanting to use joins for a while, but I'm having trouble visualizing the output so I know how to put it to use. Let's say I have 2 tables: CREATE TABLE Cities ( id INT UNSIGNED PRIMARY ...