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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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 ...
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1k views

Getting the data from a foreign key table

I have a table that relates a user to client using both their table id's UsersClients Table --------------------- | userid | clientid | --------------------- | 2 | 32 | | 3 ...
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791 views

Is there a workaround for lack of support of cascade triggers with MySQL?

As things stand, cascaded foreign key actions do not activate triggers with MySQL. I don't want to get into the debate as to whether or not this is good, I just would like to know whether there is a ...
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330 views

Foreign Key constraint on fixed value field - Ever appropriate?

I have a short (15 rows) look-up table that lists the valid values for several columns in the database. I don't think it can be considered a One-True-Lookup-Table, it is about a single definite ...
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407 views

Foreign Keys with Composite Key

Imagine I have a table with the following dependency: (Name, BoughtFrom, TimeBought) --> Cost Where the three attributes in bold form a composite primary key for the table. Now then, I want to ...
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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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How to represent class table inheritance (current DBMS-specific way please)?

I want to implement class either-or table inheritance (Account, CatAccountDetails, DogAccountDetails) in SQL Server. I found a recommendation for MySQL here (How do I map an IS-A relationship into a ...
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2answers
615 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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What alternatives exist when a table requires too many foreign keys?

We have a base table that defines parts and holds information like part number, description, price, weight, etc. We also have approximately 400 tables that reference the base table and provide ...
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Foreign key constraints with MySQL/InnoDB

I am try to do some performance testing with varchar foreign keys vs int foreign keys and was wondering how foreign key constraints effect performance of MySQL. I assume that they effect ...
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4k views

How to retrieve foreign key constraints data

I'm looking for a query allowing to retrieve foreign key infos (each line: referrencing table & field, referrenced table & field) of an entire schema. I've found this, but does not gives all ...
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330 views

Is it possible to check all constraints in a MySQL database?

MySQL offers the ability to temporarily disable the foreign key checks, thus allowing inconsistent data to enter the database. Is it possible to check an entire MySQL database, table by table, row by ...
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710 views

Missing PK/FK after database migration

We recently had a server migration. A new server is now the PROD server, and what used to be the PROD server is now the staging environment. Apparently, the data was transferred correctly, but the ...
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180 views

Multiple primary keys

I am new to database design and have been looking at some example data models here. One thing I don't understand is if you have a table like client_addresses from the link above: ...
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1k views

MySQL 5.5.8 InnoDB Foreign Key, JOIN performance

We are using aws/rds, MySQL 5.5.8. all InnoDB. For performance purposes, we have merged some data-elements into varchar fields; mini-sized int and date type fields; added covering indexes; ...
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1answer
62 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
789 views

Dump PostgreSQL schema with foreign keys and referenced data

The official PostgreSQL documentation states that pg_dump can use the --schema=SCHEMA option to selectively dump a given schema. However according to the same documentation (read Note on ...
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1answer
205 views

Symmetric self-referential many-to-many

I'm trying to model a hierarchy of categories where a category can have multiple parents ( an overlapping tree model as described in this book ) I have the following tables video_categories int ...
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1answer
1k views

How do you avoid a foreign key constraint creating deadlocks?

So I have two tables that create a deadlock. The application literally do nothing but update two different tables in two different transactions. There is a foreign key constraint (not cascading, just ...
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1answer
7k 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
2k views

Setting up a Postgresql Partition with foreign key

I have a Ubuntu 12.04 Server with PostgreSQL 9.1 installed. I am trying to setup Partitioning on a existing Postgres DB(say 'xyz') which has very huge tables and some have foreign keys set on them. ...
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154 views

Ok to drop indexes on FK's if they have no stats in the DMVS

I have used the well known query below from Kevin Kline to check for unused indexes. Several indexes created on Foreign keys returns no read stats, only writes. Are you 100% safe to drop these ...
3
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1answer
159 views

Optimised Schema for City-to-City Distance Table

This is my first question, forgive me if this question is simple. I'm stuck here, trying to implement the relations for the data represented below. I want to scale it vertically (new rows), instead of ...
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1answer
2k views

Performance tuning a cascading delete with many foreign keys

I have a delete query that is taking a long time. Looking at the execution plan, I see that most of the estimated cost in the delete query is in a section of the data model that had a lot of data ...
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1answer
3k views

Foreign key of multiple tables

I have the following 3 tables: ╔═════════════════╗ ║ Companies ║ ╠═════════════════╣ ║ id ║ ║ name ║ ║ type ║ ║ etc... ║ ╚═════════════════╝ ...
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Tablestructure for fast inserts/deletes with foreign keys

Current Situation We have a table called c with ca. 300,000 rows. In this table we store the competitors for a specific product. Example: id | competitors | some infos about competitor | ...
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Generate insert statements for table AND related data

I'm looking to move data from tables and related tables between 2 databases. The trouble is the primary keys are out of sync. Is anyone aware of a tool which can generate insert statements for a ...
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1answer
120 views

Can I place the attribute in the Entity, when the foreign key is also already present?

I am using DBdesigner Fork for generating ER diagram. I have the 'Company' as an entity for which can I place the attribute of 'idShares', despite of having the foreign key of Shares Entity in the ...
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PostgreSQL - insert/update violates foreign key constraints

I am a new one in postgreSQL. I have 3 tables, one table references the other 2 table's primary keys. But I couldn't able to insert data into the Table3. See the code below : DROP TABLE Table1 ...
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67 views

View for a MANY_MANY_MANY relationship

Let's say I have 3 main tables: category, tag, url category and tag have a MANY_MANY relationship (category_tag). tag and url have a MANY_MANY relationship (url_tag). I would like for a given ...
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2answers
5k views

How to make a trigger that will compare input with a value of other table?

I had made two tables with the following fields: TABLE 1: "Bookings" FIELD: "fk_flight_number" FIELD: "date_of_reservation" TABLE 2: "Flights" FIELD: "flight_number" FIELD: ...
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1answer
201 views

Pitfalls of creating a foreign key constraint on a system table?

I have a number of tables which hold metadata about the tables and packages in the system. This is intended to be a resource for analysts and documentation so it is not used to create data. One of ...
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1answer
108 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
508 views

MySQL Unique Index Keylength

I am hashing keys from one table that provides a 256 bit (64 char length) alphanumeric string that I intend to use in a second table as a foreign key. The engine of choice here is InnoDB. There are ...
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1answer
152 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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Classes and objects (but not ORD)

I am looking for help laying out a database that stores information similar to a class definition and then also instances of those 'classes' (but not referring to an ORD). The specific example is ...
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1answer
148 views

SQL Server 2005, Foreign key check against part of a table

I have an articles table that references a categories table. I'm defining the foreign key like this: constraint fk_categoryid foreign key (categoryid) references categories (categoryid) on update no ...
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1answer
187 views

Are these custom module Drupal tables lacking foreign keys? mysqldump with table structures without data is included

I am troubleshooting a some tables in MySQL used by a custom Drupal module. Documentation for these tables is poor so I used mysqldump to get the structures in the Drupal database without the data. I ...
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3answers
433 views

Mysql error while creating FK

here is structure of both tables category table CREATE TABLE category ( `catID` bigint(20) NOT NULL AUTO_INCREMENT, `title` varchar(60) NOT NULL, `created_at` timestamp NOT NULL DEFAULT ...
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1answer
3k views

Will FK ON UPDATE CASCADE work?

Intuitively, adding the option ON UPDATE CASCADE to a foreign key constraint will have the effect of updating all referencing columns with the updated value of the key. Would that really work? ...
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1answer
129 views

Unique foreign key constraint between three tables

I'd like to track appointment attendances. Visitors can have appointments, or they can just turn up. If they have an appointment, and miss it, in which case I'd like to record a reason for the missed ...
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1answer
82 views

How to get dependencies order

I have a Database Called Total and I have about 40 tables in it.I am trying to move the tables in the database into a different server So I have prepared all the create table scripts but the problem ...
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1answer
1k views

foreign key constraints on same table

I have a table structure like this. tblquestion ( nQuestionId1 INT UNSIGNED PRIMARY KEY AUTO_INCREMENT NOT_NULL, nQuestionId2 INT UNSIGNED ALLOW NULL ); Here..nQuestionId2 has a foreign key ...
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Using Multi-table Insert for Parent and Child Table

Is it safe to use Oracle's multi-table insert statement to insert into a (foreign key constrained) parent and child table? With minimal examples, I've found that it works as long as the parent table ...
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1answer
4k views

disable constraints before using pg_restore.exe

When I try to execute pg_restore.exe of a dump file from a database, it throws dozens of errors, all the same: ERROR: insert or update on table "someTable" violates foreign key constraint ...
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2answers
169 views

How do automaticly delete rows from other tables

I have a MySql DB. I have a table - recipes. Also have 2 tables -ingredients and instructions. both have for each entry - a foreign key to the related recipe. I want that when I delete an entry from ...
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2answers
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Primary key vs. unique index: performance difference with foreign keys?

Will there be any difference in performance if you compare a query fetching data via a join between two tables where there's a relationship against either of the following: A primary key A unique ...
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1answer
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Constructing Circularly Referenced Tables

I'm attempting to construct two tables in Oracle, A and B; each of these tables reference each other. In my script, I have the foreign key constraints 'in-line' of the create table statements. Of ...
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Will a delete then insert within a transaction cascade?

I had a question about what the expected and actual behaviour for the following scenario is. The scenario is one where a database table ([table1]) is cleared and reloaded every day. The table has an ...
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1answer
854 views

How can I check the integrity of disabled foreign key relationships for each individual table? (SQL Server 2008)

I'm porting a huge legacy database that many different legacy frontends depend on. When I'm finished, a new frontend will be running alongside all the old legacy frontends minus the frontend I ...