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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Check attribute table referenced foreign key

I have two tables a and b like this: a: id, type b: a_id, ... There is a limitation for which the references of a in b can only be those which have type equal to a limited set of values. Is it ...
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2answers
153 views

Can I use `on delete set null` on a compound foreign key which contains a primary key column?

The docs say: Restricting and cascading deletes are the two most common options. RESTRICT prevents deletion of a referenced row. NO ACTION means that if any referencing rows still exist when the ...
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1answer
49 views

Query perfomance with multiple JOINs on MyISAM-based DB

I'm working with Enron Email Dataset in MySQL database. After I executed data import from the dump file into MyISAM-based DB, I got the set of tables without any connections between them via foreign ...
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118 views

How to I establish a 1 to 1 relationship

I have a table Nurse: CREATE TABLE [dbo].[Nurse]( [EmployeeId] [int] IDENTITY(1,1) NOT NULL, [WardId] [int] NOT NULL, CONSTRAINT [PK_Nurse] PRIMARY KEY CLUSTERED ( [EmployeeId] ASC ...
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2answers
244 views

What's the use of assigning foreign keys on MySQL [duplicate]

Aside from indexing the value of the foreign key, what is/are the advantage of assigning foreign keys to databases? I've seen a lot of databases that does not assign foreign keys, but is relational by ...
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1answer
42 views

Move Commonly-Repeated Fields into a new Table

I'm still at the design stage for a new system, and I've noticed there are several places where different types of object share similar fields. In this case, we have customers, offices, warehouses ...
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1answer
156 views

Foreign key double inheritance SQLITE

I'm designing a domotic system database and I'm trying to figure out how to represent two foreign keys. This is the cardinality I want. Consider 1...N Areas (rooms, halls, kitchens, etc.): Area 1 - ...
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1answer
70 views

Why use foreign keys if cascade action is not need?

I'm testing some queries with MySQL and tried to create two tables were there should be a reference between IDs. Something like: CREATE TABLE user ( id int(11) UNSIGNED AUTO_INCREMENT, name ...
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1answer
168 views

CentOS and Ubuntu differences with information_schema

I have a Vagrant VM running CentOS 6.5. My localhost is Ubuntu 12.04, both running MySQL. I have the exact same database on both (structured exactly the same, different testing seed data in both). ...
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1answer
146 views

Multiple source CASCADE DELETE behavior

I'm having trouble understanding Postgres's CASCADE DELETE behavior. If table_A REFERENCES table_B, and the column referenced could have multiple instances of the same value, will the table_A row be ...
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1answer
5k views

MYSQL - Problem with foreign keys on same table

In Mysql 5.5, I have a table, in which I store some informations about "events".. In order to have a chronological order, I made two columns that reference to the previous and to the next event. So I ...
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2answers
89 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 ...
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1answer
26 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 ...
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1answer
2k views

Foreign Key - One Child Table to Multiple Parent Tables

Maybe I'm thinking of this problem in the wrong way, but we maintain an AccessControl table that is a child to several parent tables (e.g. CompanyItems, SystemFiles, etc.). I'm trying to make sure we ...
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2answers
705 views

Naming foreign key columns

Now I hear that the best practice for naming foreign key columns is the name of the table and field (and maybe the function if there are multiple foreign keys to the same table), for example, a ...
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2answers
553 views

Merging Results while avoiding Key Constraint Error?

I have a table with a primary key which is two integer fields, each a foreign key to a different table. (Multi to Multi table) In one of the foreign tables two rows are merged and this table is ...
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1answer
17 views

Aruba-MySQL: can't create/change table to engine=INNODB

We have our database stored in aruba (mysql.aruba.it) where there is a table called "task". Because of many changes in the requirements we decided to drop the table and create it again from 0 with ...
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2answers
47 views

MySQL - Creating an associative table

I have the following table structures: Cases: (PK) case_id | case_notes | time 1 | blah | timestamp 2 | blah | timestamp 3 | blah | timestamp . | . ...
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1answer
190 views

ON DELETE CASCADE not deleting entry for foreign key

I am running the below query in ideone CREATE TABLE AUTHOR ( AUTHOR_ID NUMBER(5) PRIMARY KEY, AUTHOR_NAME VARCHAR2(18) ); INSERT INTO AUTHOR (AUTHOR_ID, AUTHOR_NAME) VALUES (1234, 'MC GRAW HILL'); ...
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1answer
336 views

adding autoincrement to id already part of foreign key

I would like to add the autoincrement property for all my table's columns named id in a schema. However, most of them are part of a foreign key constraint. Is there any other way to do it without ...
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2answers
360 views

insert inserted id to another table

Here's the scenario: create table a ( id serial primary key, val text ); create table b ( id serial primary key, a_id integer references a(id) ); create rule a_inserted as on insert to a do ...
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1answer
42 views

can I use many-to-many relation with weak entity

I have an entity, for example employee(key employee ID), and every employee can have multiple responsibilities. Every responsibility can be tasked to multiple employees. I have 3 options: 1) Create ...
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1answer
91 views

MySQL #1005 - Can't create table 'startet' (errno: 150)

Can anyone figure out why phpMyAdmin won't create the last table? It works fine if I drop the last foreign key, but I need it in there to get my assignment approved... CREATE TABLE nasjon ( ...
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1answer
38 views

multi-column FKs with NULL values

I understand that in PostgreSQL if there is a multi-column FK from table B to table A and one or more of the FK columns in table B are nullable then the FK is still considered as "honored" for the ...
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1answer
142 views

create foreign keys for pivot tables

I'm trying to optimise and speed up a mysql 5.6 datatabase. I have two tables with a many to many relationship: Reservation and Resource. Each Reservation can have many Resources and each Resource ...
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3answers
453 views

Mysql Create table shows ERROR 1005 errno 150

I am trying to make a junction table, but I getting a ERROR 1005 errno 150 CREATE TABLE 61furiousFistPokemon( cardNumber int NOT NULL PRIMARY KEY, pokemonName VARCHAR(12), type VARCHAR(10), stage ...
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1answer
57 views

Query executes fast, but keeps the table locked for some time

Executing the following query is very fast (75ms), but removing the comment from the last row it becomes slow (2.5s), and the time increases exponentially with the number of rows in the table. It ...
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1answer
64 views

Save dataset within another table best practice

I want to save one dataset within another table, this dataset should be persistent. For example Table1: FIELDS (A,B,C) Table2: FIELDS (D, DuplicateTable1) I can think of 2 possiblities: Have ...
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1answer
137 views

Implementing a simple ERD in MySQL: is the implementation below 100% compliant with the ERD?

ERD Consider the following ERD: Tables From it, I derived the following tables: Company ------------------ c_id c_name ------------------ CompanyEmail ------------------ c_id ...
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1answer
37 views

Insert / Edit Rows by Selecting FK row

When inserting or editing rows ("Edit Top 200 Rows") for a table with a FK constraint, can the editor be configured to select the foreign row, rather than me having to look up the FK?
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2answers
74 views

MySQL foreign key error

I need to update rows in a child table,but I am getting following error while I run the code, Company Table CREATE TABLE `company` ( `Company_id` int(11) NOT NULL AUTO_INCREMENT, `Company_name` ...
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1answer
371 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
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1answer
390 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 ...
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2answers
58 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 ...
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1answer
106 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 ...
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1answer
1k 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) ) ...
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2answers
984 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 ...
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1answer
74 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 ...
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1answer
695 views

Retrieving all PK and FK

I have a big database that I need to extract all primary keys and foreign keys from each table. I have pgAdmin III. Is there a way to do this automatically and not go over each table manually?
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1answer
66 views

Check for records that break a foreign constraint (created with foreign_key_checks = 0)?

Is there an easy way to check for any records in a table that breaks any constraint? The constraint was created on a populated table using "foreign_key_checks=0".
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1answer
8k views

To drop a table, do I have to drop all foreign key constraints or can I just NOCHECK them?

I know you cannot drop a table that has active foreign key constraints. So I was wondering is it safe to: ALTER TABLE myTable NOCHECK CONSTRAINT all DROP TABLE myTable Rather than dropping the ...
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1answer
674 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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1answer
109 views

Is it acceptable to have a surrogate/primary key of one table be the primary/foreign key of another table?

For my purposes I'm trying to apply this to Microsoft SQL, but would like to know if there are restrictions for other DBMS regarding this. I don't know how to represent UML as ascii characters so if ...
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1answer
159 views

Handling error of foreign key

How to set a FK value NULL upon receiving error for foreign key constraint? Consider a simple table a CREATE TABLE test ( id int(11) NOT NULL AUTO_INCREMENT ex_key int(11), FOREIGN ...
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2answers
2k 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. ...
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1answer
35 views

Problems in Choosing Foreign Keys :S

I am designing my very first relational database. I am now in the conceptual design, building tables and views, selecting the primary and foreign keys and normalizing everything. But now, I am stock ...
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1answer
36 views

Multiple Cascade Paths (Not really) - Sql Server

In my database I have a table with 2 columns referencing the same column in a separate table. I know this creates a race condition, but I have a check in place to make sure they don't point to the ...
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0answers
40 views

What order do foreign key constraints run in? Why does my foreign key not work after import?

I have two tables tags and tag_memberships in a PostgreSQL database. On the tag_memberships table, I have two constraints. The first is this: ALTER TABLE tag_memberships ADD CONSTRAINT ...
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2answers
43 views

Performance impact of adding a foreign key to a 1M rows table

I have an ecommerce database running MariaDB + InnoDB, which has a table to store the transactions (T) and another which stores quotes (Q). I'd like to make a connection between T and Q by adding a ...
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0answers
30 views

Sybase: Delete foreign key IF exists fails

I've a database, on which we will have to delete of tables/foreign keys/view. We did deleted all the required element in PowerDesigner, then we did the "Apply model change to the database". We ...