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.

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3answers
278 views

Normalization: 'zip code' as a primary key

I've seen frequently that you should not have all address fields (zip, street, city, state, country, etc) in the same table as your user info table (pk_id, name, email... ). This would be in ...
2
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1answer
674 views

Need for indexes on foreign keys

I'm struggling with indexes, primary keys and foreign keys... And the need of having them all. If I have two tables, both of them have an integer as a primary key. The first table references ...
0
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1answer
116 views

Implementing foreign keys on generalized data model

Suppose the ASCII tree below is a UML generalized concept model. To represent these entities/classes in UML, lets assume [mammal] a super class, and the level 1 classes, [wild] and [domestic] are sub ...
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2answers
134 views

How to normalize data en-masse?

Goal: Extract address fields from a users table into a separate addresses table linked by foreign key. I have created the structure below, and have millions of rows to deal with. I need to do this ...
5
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2answers
4k views

MySQL, foreign key, can't create table error 150

UPDATE: Sorry, it was because i forgot to add UNSIGNED attribute to the lang_id column. Original: I'm trying to create a table with foreign key in MySQL. I get this error: #1005 - Can't create table ...
3
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2answers
142 views

Pair of 2-tuple composite FKs pointing to same table (closure table pattern)

I don't have much experience with DB design, and having a hard time figuring out what's wrong with the following: Table father has a composite PK (col1, col2) Table closure has ancestor(a-col1, ...
0
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1answer
26 views

Good idea to include summary of frequently accessed data from another foreign-keyed table?

Sorry for poor title, I'll try to explain it in more detail here. I have an application that often gets a row from table A, then looks up a column from that in a foreign key mapping table (table B), ...
2
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3answers
326 views

Many to many link tables with history? [closed]

While creating a PostgreSQL database of customer subscribed services with DNS domains, I want to: enable customers to subscribe to multiple services each service can have multiple domain names per ...
0
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1answer
128 views

Get unmatched rows for foreign key

Consider two tables: CREATE TABLE Users( id INT PRIMARY KEY, name VARCHAR(128) ) Engine=InnoDB CREATE TABLE Tags( id INT PRIMARY KEY, user REFERENCES Users(id), tag VARCHAR(128) ) ...
0
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2answers
60 views

Foreign key for rows added later

I'm using a queue to crawl pages and track links between them. I have a table called page with a primary key called page_id. I have a table called links with two columns: link_from, link_to The ...
0
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0answers
78 views

Need advice on this EER Diagram

This db will work with a CakePhp app and need advice about design. Is it good idea to put orders on center or should I put clients on center? Clients has orders and an order record can only have one ...
0
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1answer
115 views

Can a foreign key have a default value equal to 0?

I have a column whose default value is 0 .Can I make that column as foreign_key
0
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2answers
50 views

Guaranteeing a FK relationship through multiple tables

I'm using MySQL / InnoDB, and using foreign keys to preserve relationships across tables. In the following scenaro (depicted below), a 'manager' is associated with a 'recordLabel', and an 'artist' is ...
0
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2answers
1k views

Delete rows in parent table based on criteria in child table - Oracle

I have a table B with a foreign key to table A. I want to DELETE some rows in table B, and I also want to DELETE their parent rows in table A. However, the delete criteria is based on table B. The ...
1
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1answer
452 views

MySQL: update instead of delete if foreign key constraint?

I have a bit of a strange question. I know about insert on duplicate key update. My question is, is there something similar for deletes that fail because of foreign key constraints? For example: ...
4
votes
1answer
288 views

How to relate two rows in the same table

I have a table where the rows can be related to each other, and logically, the relationship goes both ways (basically, is directionless) between the two rows. (And if you're wondering, yes, this ...
0
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1answer
284 views

Mysql foreign key cascade delete

Does mysql have a way to delete all sub links if a row was deleted from a "parent" table? Example table setup is below, the issue I am trying to avoid is having to maintain a script that deletes the ...
1
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0answers
164 views

How can I look up table relationships in SQL if I don't have physical/logical models? [closed]

What is the best way to look up/learn table relationships in a database that I'm not familiar with and I don’t have any Logical/Physical models available? Is there a tool that I can use? I’ve been ...
2
votes
1answer
79 views

Is it necessary to drop foreign keys before adding a null column to a table and then re-add them?

I have generated some SQL Server(2008) upgrade scripts using SqlCompare. The primary objective is to add a null column. However, the generated script wants to drop foreign keys in a couple of other ...
1
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1answer
3k views

“Cannot add or update a child row” when deleting a record?

I have the two following tables: survey_main ---------- id name answers_main -------------- id survey_id I have the following foreign key constraint on the answers_main table: CONSTRAINT ...
1
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1answer
127 views

How to link a customer to a country when the city/state isn't known

We have a situation where medical systems are sold to hospital groups, but at the time of the order, we don't always know into which state and city the system will be installed. We always know the ...
1
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1answer
2k views

Converting ER diagram to tables and relationships in sql

Department : Branch is 1 : M Branch : Course is 1 : M Branch : Student is 1 : M Branch : Applicant is M : N Applicant : Student is 1 : 1 These are the conditions prescribed in the ER diagram. ...
1
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1answer
1k views

Removing foreign key when it is not named

I've created a table named 'student' as : create table student( stud_id number primary key, stud_name varchar2(30) not null, branch_id varchar2(4) references branch(branch_id), course_id ...
2
votes
2answers
810 views

Two primary keys to one foreign key

racing_couple ID (PRIMARY) breeding_couple ID (PRIMARY) egg IDpar(FOREIGN KEY) I have 2 IDs from 2 different tables (racing_couple and breeding_couple) and they are primary keys. In 3. table (egg) ...
-2
votes
1answer
661 views

Cannot create FOREIGN KEY for a table [closed]

I'm not a professional DBA, I encountered a problem when I's attempting to create FOREIGN KEY for a specific table by the following SQL script (I'm using MySQL): ALTER TABLE mmy_answer ADD CONSTRAINT ...
1
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1answer
203 views

Multiple foreign keys with shared columns for weak entities

this is my first question at stackexchange. I have a parent table (P) with two child (CC and CD): CREATE TABLE P ( A CHAR(3), B CHAR(2), CONSTRAINT PK_P PRIMARY KEY(A, B) ) CREATE TABLE CC ...
4
votes
3answers
21k views

How do I insert a row which contains a foreign key?

Using PostgreSQL v9.1. I have the following tables: CREATE TABLE foo ( id BIGSERIAL NOT NULL UNIQUE PRIMARY KEY, type VARCHAR(60) NOT NULL UNIQUE ); CREATE TABLE bar ( id BIGSERIAL ...
0
votes
1answer
69 views

Foreign key in MySQL

I am learning about database, I need to know something about the foreign key in MySQL. Consider the following two tables. UserGroupType. UserGroup. UserGroupType: UserGroup: In this table ...
0
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1answer
269 views

Modify MySQL foreign key related column without dropping foreign key relation

I need to modify a foreign key related column. When I tried to alter it I got "Error on rename of 'x' to 'y' (errno: 150)" error. So I googled and found foreign key relation is the 'villain'. I ...
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votes
1answer
172 views

How to represent it with UNIQUE indexes and foreign keys?

"Group" is a group of pupils. "Topic" is a topic of lessons. To every group corresponds exactly one topic. (So there may be multiple groups per topic.) To a pupil corresponds multiple groups, but ...
2
votes
1answer
1k views

prevent MySQL Workbench to add index for foreignkey constraint when it is first part of primary

I know for each foreign key we should make an index on its column, But it is not necessary when that column in first part of PRIMARY index. MySQL accepts this query: CREATE TABLE IF NOT EXISTS ...
13
votes
1answer
2k views

How to write a query which finds all circular references when a table references itself?

I have the following schema (names changed), which I cannot change: CREATE TABLE MyTable ( Id INT NOT NULL PRIMARY KEY, ParentId INT NOT NULL ); ALTER TABLE MyTable ADD FOREIGN KEY ...
7
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2answers
10k views

Good explanation of cascade (ON DELETE/UPDATE) behavior

I don't design schemas everyday, but when I do, I try to setup cascade updates/deletes correctly to make administration easier. I understand how cascades work, but I can never remember which table is ...
2
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1answer
1k views

If foreign keys/cascade deletes are bad, why use a database-server with that feature?

I noticed wordpress/rails etc do not use foreign keys constraint or cascade deletes features from database. Instead they handle this in PHP/Ruby/scripting level! I have read this and this. Most ...
3
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2answers
1k views

Auto-increment key and Foreign Key as composite for relational database

I do not have any experience in databases other than what I have from just playing with workbench and trying to understand how I need to setup this database for a project. I have been searching the ...
0
votes
1answer
491 views

HOW to “SUM” and “JOIN” for single query of a poll results?

I have a poll database as CREATE TABLE poll_answer answer_id, answer varchar(255), poll_id int(11), FOREIGN KEY(poll_id) REFERENCES polls(poll_id) ON DELETE CASCADE, PRIMARY KEY(answer_id) ) ...
0
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1answer
571 views

MySQL cannot create foreign key, errors 1005, 150

I'm trying to add a foreign key to a MySQL InnoDB table, linking a BIGINT with a table within the same database. I'm using MySQL Workbench to do this. It generates a script: ALTER TABLE ...
1
vote
1answer
888 views

Is it possible to force drop of mysql tables with FK?

For dropping a table in which a Foreign Key is used in other tables, it is necessary to drop all other tables having FK connection with the corresponding table. Is there a short way to drop a table, ...
2
votes
2answers
212 views

Performance effect of indexing foreign keys

My database is for an HR application with performance reviews and I am interested in whether I should index my foreign key. There are two tables involved. The first is a ratings table with 2 columns: ...
3
votes
1answer
1k views

Schema design: Use of association (aka: bridge/junction) table vs foreign key constraint with composite index containing a non-key field

This is an inventory database for IT assets. The models used are trimmed in order to focus on the problem at hand. Using SQL Server 2008. Thanks for taking the time to read and for any input you can ...
2
votes
1answer
2k views

Insert Row With Foreign Key Equal to ID - Circular Reference

In MySQL database I have an events table which has a circular reference to itself with the following columns. id (PK) | user_id (FK) | event_id (FK) | title Each new row inserted has a circular ...
0
votes
1answer
39 views

Table Design for user-specific and user-agnostic criteria

I want to design a table that is general enough to accommodate an increasing number of achievements as I come up with new accomplishments to reward. Initially, I thought to design the table as ...
1
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0answers
34 views

A separate table or ENUM? [duplicate]

There is a table person (which has among autoincremented primary key field id such fields as firtsname and lastname). There is a table employee whose primary (but not autoincremented) personid is a ...
5
votes
1answer
116 views

Many:Many with Shared Relation

I'm modelling data with multiplicity like this: Each Composition/Anthology related pair must share a Composer. Also, each Anthology must contain at least one Composition. How would you recommend I ...
1
vote
1answer
189 views

Foreign Key to Multicolumn Primary Key?

I have three connected table in my design. Basic logic is when a category deleted, also delete records in category_product table which has deleted category's id in its cat_id column. But when I tried ...
1
vote
1answer
305 views

Table for optional parent/child relationship

Assuming we have the following table: Item, Parent, Child and Parent is the parent of child. The item can either belong to a parent or child and not both. I have other tables that are similar to ...
0
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1answer
65 views

best relationship for this design?

There is a table users with autoincrement primary key id. There is also a table employees (every employee is a user but not vice versa). The employees primary key is userid. The field userid is not ...
0
votes
1answer
23 views

Which of tables key to reference?

MySQL. There is a table users with autoincrement primary key id. There is also a table employees (every employee is a user but not vice versa). The employees primary key is userid. The field userid ...
2
votes
1answer
99 views

How to enforce a nullable foreign key?

I have a relation between two tables. The foreign key table can have a row related in the primary table. There's a way to enforce the value of the FK column to be NULL or one of the values of the PK ...
1
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3answers
71 views

What is the benefit of two FK, when one of them can be deduced from another table?

The third party Microsoft SQL Server database I'm working on is using the structure which can be illustrated with this example: Let's take three tables: Shop which is the topmost level and ...