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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Determining Homogeneity by Common Foreign Keys

I manage a MySQL database of ten or so tables. In higher code, I have a list of primary keys belonging to entries of some table A. These A entries have foreign keys to entries in another table B. The ...
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135 views

More Details for MySQL's errorno:150

When MySQL can't create a table due to a foreign key constraint problem, it returns the following error Can't create table 'dbname.table_name' (errno: 150) Is there anyway to have MySQL tell you ...
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4k views

How to insert data into tables which reference each other?(MySQL)

I'm a student and right now I have a problem that I couldn't solve by myself(after searching on the Internet). I'm not going to give my «homework» because I want to learn what I'm doing but I will ...
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134 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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2answers
347 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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219 views

Proper implementation of child (derived) table PK/FK during single and multiple inheritance hard coded generalization physical data model

Below is an image of hard coded generalization UML logical model of entities. I'd like to implement these classes as tables in a physical data model. Two derived classes/entities (Class2 and ...
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1answer
2k 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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2answers
175 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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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. ...
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3k 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 ...
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1answer
444 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 ...
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2answers
177 views

Usage of foreign key when the referenced table data will not change

I have to design a table where user has 10 fields and 6 are dropdown. Some are single selections and some multiple. Dropdown data is supposed to change very rarely. For e.g., the user is presented ...
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2k 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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936 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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2answers
369 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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1answer
123 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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2answers
8k views

Foreign Key Constraint fails

I have the following tables: // Base Scans CREATE TABLE `basescans` ( `id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT, `name` VARCHAR(100) NULL DEFAULT NULL, `status_id` INT(10) UNSIGNED ...
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Is it possible to cascade delete a column value? [duplicate]

So say I delete catID from table A and table B has the same foreign key value? It's hard to explain so I'll try and show you with the two images below: items table Is it possible to delete the ...
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58 views

How to pass the value of PK to FK

Ok, so here it goes. I have a table called employee. then I have another table called languages. I need to copy the value of PK of employee table to foreign key in Languages table, rather than ...
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1answer
91 views

How to resolve foreign key references across different databases (iSeries and SQL Server)

I've got a system that has a DB2 iSeries database. We are rewriting a portion of the system and implementing it using SQL Server and Entity Framework. Originally, I was lead to believe that there ...
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33 views

Update all foreign keys to a different primary key

In a MySQL database, I have a table full of business information. Lots of businesses have been inserted twice due to human error, so the same information exists with two different primary keys. ...
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42 views

Can you enforce uniqueness in MySQL based on column in foreign table?

I am refactoring one of my database tables and I've come up with an issue. Specifically, I have a table with four columns. We'll call the first three my.a, my.b and my.c. I have a uniqueness ...
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21 views

Compound key that only allows nulls if they are null in the referenced table

I want to create a compound foreign key constraint that only allows a null value in one of the columns if there is a matching row with a null value in the referenced table. Additionally, the ...
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42 views

Implementing a consistent mailbox

I am trying to implement something like a mailbox for short messages between users. I am using Postgresql 9.4.1 with SQLAlchemy (Python3). There is a table of users: users = Table('users',metadata, ...
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MySQL - Cannot add new Foreign Key

I'm using magento and it does some re-index for a product flat table structure. In this process a new table is created. The SQL for that table is something like: CREATE TABLE ...
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95 views

How to write a query which recursively returns all foreign key references to a column?

I need to obtain a list of foreign keys which refer to a given column, as well as all foreign keys which refer to those keys, and so on. Order does not matter. I have SELECT s.name, t.name, ...
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79 views

Select all foreign key relationship chains from any set of potentially gapped table names

I am using this query to find all foreign key relationships: SELECT con.relname AS child_table, att2.attname AS child_column, cl.relname AS parent_table, att.attname AS parent_column ...
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102 views

Is it best practice to include partition keys within foreign keys when referencing partitioned tables?

The large tables in our database are partitioned by an id in order to separate data and speed up IO. The table of the data is partitioned by the partition key, but the primary key is only on an ...
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20 views

Can I include extra columns in a m->m mapping table? [duplicate]

I guess this is sort of an odd question, but consider this scenario. table classes (id_pk) table students (id_pk) table students_classes_map (students_id_fk_pk, classes_id_fk_pk, finalExamScore ...
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1answer
164 views

Sybase ASA: Saving and dropping all foreign keys and most Primary Keys for (Bulk) Insert

Background Information: I am trying to migrate from an ASA 12 Database, to a ASA 12 Database by using a Remote Server. I have to migrate a lot of Rows (not all), spread over a lot of tables (not ...
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661 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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135 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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241 views

Multiple relationships between the same entities

Is there a name for when 2 entities can have multiple relationships between them?
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How to add FK on a column of composite type in PostgreSQL?

I have a table which contains a composite type and I am trying to connect a column of it to another table's PK. CREATE TABLE aaa (col1 SERIAL PRIMARY KEY); CREATE TYPE bbb AS (col2 INTEGER); CREATE ...
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229 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 ...
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36 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 ...
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751 views

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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1answer
213 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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43 views

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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189 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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2answers
181 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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Dealing with Invisible Referencers

Using Oracle database, suppose I have a parent table parent defined in schema A, and a child table child defined in schema B. To achieve this, schema A granted references privilege on parent to schema ...
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3answers
45 views

Reset Key Names to Defaults?

I'm working with some tables/columns that were renamed at some point, but the names of the primary/foreign keys are still based on the previous names. In SSMS is there any (preferably automatic) way ...
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2answers
12k views

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 insert data into the Table3. See the code below : DROP TABLE Table1 CASCADE; ...
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1answer
49 views

How can a primary key be inserted as foreign key?

Hi I am building an order intake form that will have information submitted belonging to 3 tables. The order table will have the primary key used for the property and customer table. How can I ...
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2answers
985 views

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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2k views

Create relationship between two tables with composite primary key

I've created a table [t1] with two fields and a composite primary key, show in below: create table t1( id int, name nchar(10), primary key(id,name) ); I want to create a second table ...
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4answers
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SqlServer: can one table's PK be the FK of other two table's? [duplicate]

I have three tables project, users and proj_user. The PK of proj_user table is the FK of project and users table's pk e.g.(project_id,user_id) My question is, is it possible for the project_id and ...
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1answer
93 views

Batch converting indexes to keys [closed]

I have a legacy MS SQL Server database where all the primary and foreign keys were created as indexes. I am developing the new version of our software with Entity Frameworks, which I have learned ...
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237 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) ) ...