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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1answer
351 views

Slow delete caused by many foreign keys

My DB has about 90 tables. Most of the tables have an UpdatedBy and AddedBy column that have foreign keys pointing back to the user table. With even moderate amounts of data spread throughout the ...
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23 views

Approaching multiple values in same column

I'm developing an Android-application that scrapes the schedule for my university and presents it nicely since the current system is a nightmare. I'm processing a lot of data and it gets down to ...
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2k views

getting SQL Error (1452): Cannot add or update a child row: a foreign key constraint fails (Unknown error code)

I am getting error with MySQL NDB Cluster 7.3.5 as described below: I have two tables: -User Profiles -User Services User services is a child table which contains foreign key constraint ...
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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
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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57 views

Spotting foreign key relations in a database that doesn't define all relationships as constraints?

At work I use a rather old MS Access database which defines some relations between tables, but does not outright define all of them. If the database application used an ORM, I would think that this ...
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356 views

Crow Feet notation and identifying -vs- non-identifying relationships

Is it possible to distinguish between identifying and non-identifying relationships using the Crow Feet notation? Case in point: In table Book, part of the book's Primary Key is a FK to the Author ...
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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
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
92 views

How to design to avoid two-way reference between two tables [duplicate]

I am having a problem with foreign keys between two tables. I am trying to model a relationship between members of a club and their relatives. This is a straightforward many-to-one relationship, with ...
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3answers
425 views

How to model a 1..1 Composition Relationship

We have a couple of entities/relationships of the following kind: Entity Event has a TimePoint The TimePoint contains time information about the event. It belongs to that event and cannot be used by ...
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2answers
142 views

Reasons for db2 foreign key error (-667) despite all rows appearing sane?

I have some csv formatted table dumps and loaded those into a new database with the tables defined by a DDL script from the source database (both acquired by somebody else so I cannot have a look at ...
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1answer
85 views

Relational modeled design to store versioned files

The scenario I have images in a database table and some of these need to be altered then re-saved(not overwriting the original) whilst providing a reference back to the original. I also save the ...
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1answer
183 views

How do I validate all my constraints in postgresql?

It seems like I have been bitten by the first bug described in the release notes of postgresql 9.3.4: http://www.postgresql.org/docs/devel/static/release-9-3-4.html I now have e.g. duplicate primary ...
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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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1answer
2k views

How can I create a Foreign Key to a Compound Primary Key with a single column?

I am working with a 'lookup' style table that is already in place, which has a compound primary key (not my design) in Microsoft SQL Server 2012. I want to add a foreign key to it in another table, ...
2
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1answer
817 views

Foreign key with multiple table options

I'm not sure if the title is very good, feel free to suggest a better one. People can "comment" on different objects of my site,similarly to StackExchange (for example they can comment on a Question, ...
2
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2answers
58 views

EAV-like table with both primary column pointing to the same foreign column

Background: I'm a programmer who, while had to work with simple databases several times, never had to work with complex ones. I.e. I'm proficient with basic stuff, but clueless about advanced features ...
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1answer
3k views

How to solve the error Msg 547, Level 16, State 0, Line 1 [closed]

Please suggest me how to solve the error How to solve the error Msg 547, Level 16, State 0, Line 1 The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "MyForeignKeyName". The ...
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1answer
736 views

Create table shows ERROR 1005(HY000) errno 150

i tried to create tables as per given in my textbook in MySQL server as follows: create table department (dept_name varchar(20), building varchar(15), budget numeric(12,2), ...
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44 views

Analyze a Database to Find Failed Foreign Key Constraints

I aggressively deleted a ton of data after using this query: SET FOREIGN_KEY_CHECKS = 0; Is there any easy way I can analyze the entire database to check to see if I have any hanging records that ...
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2answers
198 views

How to establish a Two-to-One table relationship (PK-FK-CK)?

My question is about DB design and its principles. I am working on a Python application where objects are mapped to database tables. I have Projects and People objects, mapped to their respective ...
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64 views

Why is adding a FK constraint slow in MySQL?

I'm doing some experimentation in MySQL 5.1.53 and I've run across a case that I just don't understand. CREATE TABLE A ( `pk` INT(11) NOT NULL, `fk` INT(11) NOT NULL, PRIMARY KEY `pk_A` ...
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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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2answers
1k views

Postgres - Create table with foreign key constraint too slow

I have a table called "Account" that is a heavily used table, has 17 columns and has upwards of 300,000 rows. I am trying to create a new table, "NewTable", that has a foreign key constraint to ...
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43 views

Table Field to Reference Field in Other Tables

Suppose I want to map a set of input values to database table fields E.g. employeeFirstName --> emp.fName employeeLastName --> emp.lName ... --> ... In theory I can create a ...
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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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2answers
731 views

Foreign key with multiple references

I have the following three tables in mysql database named "THE_COLLEGE" mysql> desc students; +----------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | ...
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1answer
1k views

Allow self-referential foreign keys to be null from an alter-table

I am trying to establish a hierarchical relationship between rows in an existing table. There are two fields of interest: a not-nullable primary key field id, and a second nullable field parentId. ...
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1answer
134 views

Enforcing constraints “two tables away”

I ran into some trouble modeling an electrical schematic in SQL. The structure I'd like to capture is part ←────────── pin ↑ ↑ part_inst ←───── pin_inst where "inst" is short ...
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1answer
56 views

What problem prevents well defined behavior of a foreign key on a non-unique column?

In my noob opinion, it strikes me that in a serialized environment, this shouldn't be a problem. Is that correct? If not, please explain to me why a foreign key's behavior on a non-unique column is ...
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2answers
122 views

Primary key for link/junction table with time-dependent data

I want to link two tables in such a way that for any given time period the relationship is one-to-one, but over time the relationship can change. As an minimal example, suppose I want to list the ...
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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
46 views

Understanding the output of \d <table> in psql

Say I run the following command: \d mtb.big_table I get the output shown below. My questions are: What are column modifiers? (what does default now() mean?) Under Indexes, Why do some indices ...
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1answer
2k views

Why is SQL Server using a clustered index scan for a self referencing FK cascade delete

I have made an example to allow me to show what my issue is: Setup: CREATE TABLE [dbo].[Test]( [TestId] [bigint] IDENTITY(1,1) NOT NULL, [ParentTestId] [bigint] NULL, CONSTRAINT [PK_Test] ...
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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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3answers
2k views

Is using multiple foreign keys separated by commas wrong, and if so, why?

There are two tables: Deal and DealCategories. One deal can have many deal categories. So the proper way should be to make a table called DealCategories with the following structure: DealCategoryId ...
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1answer
66 views

Better way to manage data integrity, without having too many composite FK's

I have following tables: class_table (class_id = Auto Incremented Primary Key (AIPK) of this table) user_table (class_id, user_id (AIPK of this table)) course_table(class_id, course_id (AIPK of this ...
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1answer
2k views

Why does altering a table and adding a foreign key create an extra constaint?

Edit: It was a default constraint as a result of setting a default value when adding the column. The name gave it away when starting with 'DF__'. Anyway, solved it by adding the column and manually ...
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0answers
82 views

join performance, index vs. index+foreignkey

I'm using an orm framework that handles data (and its integrity) on top of mysql. So far I ignored foreign keys because the orm handles that just fine. I recently read that foreign keys can enhance ...
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2answers
831 views

Is it bad idea to create foreign keys on the tables in a different schemas in the same database for big applications?

I am working on the transfer a big pl/sql web-based application to the dedicated server. This application is located in one schema with 70 packages of programm code. This application was made ...
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96 views

Error adding constraint foreign key to bridge table

Hi there I am fairly new to sql development. I am current following the head first into mysql book and is on chapter 6. On chapter 6 there is a table in third normal form but it does not contains the ...
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2answers
254 views

Use single table with foreign key or two twin tables for text entries?

I have a table answers that has several columns including the content iself such as ID | q_id | list_id | user_module_id | content | updated_timestamp The content column is a varchar since we want ...
2
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1answer
703 views

Two-column foreign key constraint only when third column is NOT NULL

Given the following tables: CREATE TABLE verified_name ( id SERIAL PRIMARY KEY, name TEXT NOT NULL, email TEXT NOT NULL, UNIQUE (name, email) ); CREATE ...
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3answers
439 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 ...
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1answer
1k 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 ...
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1answer
144 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
141 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 ...
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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
165 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, ...