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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VARCHAR primary key - MySQL

Currently, I have a categories table with 2 columns - category VARCHAR(50) NOT NULL PRIMARY KEY and parent VARCHAR(50). The parent column is a foreign key (FK) to the category column. This seems like ...
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2answers
60 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
69 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
38 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
78 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
52 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
116 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
105 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
2k 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
67 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
753 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
24 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
1k 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
433 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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1answer
16 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
23 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
36 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
27 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
43 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
47 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
48 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
45 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
105 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
36 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
55 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
168 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
306 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
52 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
88 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
667 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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1answer
67 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
303 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
60 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
6k 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
367 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
107 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
137 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
372 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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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. ...
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0answers
6 views

Problem in adding foreign key

I'm having an error while adding a foreign key constrain to my database. In my database, I'm having a table named user, student, staff, complaint and review. The table user contains fields such as ...
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1answer
18 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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0answers
9 views

Mysql Workbench Foreign Key problem

I'm working on a simple company database design but i can't figure out why i can't create foreign keys for some tables. Let me give a screenshot of the design; I'm trying to create foreign key for ...
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1answer
22 views

Syntax error debugging [closed]

I have a logically sound insert statement, but always getting "integrity constraint (%s.%s) violated - parent key not found" and couldn't find why I get it. Everything seems alright to me, no typos. ...
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0answers
27 views

INSERT missing FK rows at the same time

I found on this site the following SQL-Query to perform an insert (see this post): WITH sel AS ( SELECT val.description, val.type, f.id AS foo_id FROM ( VALUES ('testing', ...
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0answers
29 views

How to insert a row which contains a foreign key in mysql

Here's the original question regarding PostgreSQL. I'd like to know of a similar solution for MySql. The simplest syntax provided in the answer works fine as long as the relevant rows already exist ...
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1answer
15 views

MySQL: Is there a way to update a field so that all foreign key related fields are updated as well?

I'm assuming the answer to this question is yes but it is hard to Google this type of question and not get overly ambiguous results. I am working with a database that was dumped from a Magento ...
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1answer
22 views

Which foreign keys do I use if they are repeated

I have the following two tables company_relationships |ID|Company_ID|Affiliate_ID|<Relationship Info>| +--+----------+------------+-------------------+ jobs |ID|Company_ID|<Job Info>| ...
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41 views

insert record to child table which doesn't map to parent table - possible?

Actually I've 2 relevant questions: insert record to child table which doesn't map to parent table - possible? ON DELETE NO ACTION - when a record in parent table is deleted, it should affect ...
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0answers
26 views

how to disable and enable foreign key constraints for a table in sql server [duplicate]

can i disable the foreign key constraints for temporary time in SQL SERVER 2014? and how to enable the same constraints back? also i don't want to enable or disable constraints for all tables. i want ...
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0answers
15 views

MySQL - Foreign Key Problem [duplicate]

I'm trying to get to grips with Foreign Keys in MySQL (5.6), and can't figure out why the below doesn't work: CREATE TABLE `test`.`parenttable` ( `id` INT UNSIGNED NOT NULL AUTO_INCREMENT, ...