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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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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1answer
35 views

Help on MySQL joins

I'm building a system to monitor currency prices. Part of my database structure looks like this: My system is trying to pull the api ticker for each exchange with this query: SELECT distinct ...
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0answers
122 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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1answer
35 views

alternative foreign key syntax

in mysql you can assign primary key constraint to a column using two different syntax: after the column is defined, separated by coma, optionally in a new line id int auto_increment, primary key(id) ...
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2answers
103 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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0answers
68 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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0answers
28 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 ...
3
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2answers
225 views

Foreign key without referenced columns specification

I noticed in the SQL Server documentation that the list of referenced columns is not a required parameter of a foreign key constraint: <column_constraint> ::= [ CONSTRAINT constraint_name ...
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1answer
3k views

Composite primary key from multiple tables / multiple foreign keys

I want to build a composite primary key made up of foreign keys from two different tables. I'm still pretty green to this... A great answer was given to building a composite key from multiple foreign ...
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1answer
168 views

Should an INSERT cause an exclusive lock on a foreign key?

I'm working on a deadlock issue. Process A is doing a simple INSERT into TableA which has a FK to TableB Process B is doing a complicated SELECT on a join that includes TableA and TableB I'll ...
5
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1answer
3k views

Many to Many and Weak Entities

I have an entity that cannot exist without being defined by another, and I want this entity to participate in a many-to-many relationship. Example: An artist has an album (the album cannot exist ...
2
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1answer
1k views

Why dropping all foreign keys from a script is not working? [closed]

I have sysadmin rights on a SQL Server 2008 R2 box. I found a script that can drop all foreign keys and re-add them for us when we need to after a testing import. So I execute the below code with no ...
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4answers
109 views

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 ...
2
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3answers
531 views

What is the optimal solution for converting a database schema?

I actually want to get rid of the existing constraints in the database which I know sounds crazy but we are upgrading our application to a new framework which relies on the foreign key constraint ...
1
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1answer
78 views

“Transitive” keys

I have a central table, A, which will have a key that I'll call A_ID. Now, I have a table B in a "one to many" relationship with A (many B's map to one A). Each link will, of course, have a link ...
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0answers
17 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, ...
0
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1answer
568 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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2answers
262 views

Postgresql - Do Foreign Key Constraints Automatically Create Indexes?

Per the PGSQL 9.3 docs: Because this is not always needed, and there are many choices available on how to index, declaration of a foreign key constraint does not automatically create an index on ...
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0answers
32 views

See indices implicitly created for foreign key constaints in MySQL

When I add a foreign key constraint to my table, SHOW INDEX doesn't show any new indices, but the overall space used by the indices in that table increases. Apparently, the index for the field I put a ...
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0answers
45 views

Adding foreign key to MySQL does nothing

I have two systems: a dev system and a production system. On the dev system, I added a foreign key to a table using this statement, which has been created by phpMyAdmin: ALTER TABLE ...
3
votes
2answers
496 views

multivalued weak key in ER database modeling

I was wondering since i didnt find out any clarification for this. I want to store movies that exist in different formats (dvd, bluray etc) and the price for each format differs from each other as ...
3
votes
2answers
4k views

How much do foreign keys affect performance?

I'm reviewing an SQL Server 2008R2 installation having large performance problems. Currently I'm looking into its indexes and foreign keys and have found out that none of the tables have any foreign ...
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0answers
80 views

How to populate Oracle 10g tables related via foreign key?

As the title says, how do i fill random data in tables, which have foreign key references within each other. I want to then practice all the SQL commands, like, SELECT commands, JOINS, SET FUNCTIONS ...
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1answer
306 views

deleting a table referenced by many foreign keys

I have a table that I want to drop and create again, because I want to add the IDENTITY property to a column, wich is not possible directly. The problem is that I can't drop it, because my column is ...
2
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4answers
10k views

Recursive self joins

I have a comments table, which can be simplified down to this: comments ======= id user_id text parent_id where parent_id is nullable, but might be a key for its parent comment. Now, how can I ...
3
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4answers
177 views

How do I prove that the act of removing foreign keys doesn't corrupt existing data?

TL;DR: Prove that in practice, the execution of the alter table table_name drop foreign key constraint_name statement does not corrupt existing data. The important consideration is the execution of ...
7
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1answer
2k views

MATCH FULL vs MATCH SIMPLE

I've noticed a MATCH SIMPLE or MATCH FULL option in phpPgAdmin, but I can't find a description in the docs. How do they function? The default is set to MATCH SIMPLE.
2
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1answer
89 views

Foreign key, key split in two tables

I have to record a list of events made of action, reason (optional, may be multiple), user. I have a master table with all the valid action, and another with all the valid action-reason combination. ...
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2answers
2k views

Partitioning a Table Referenced by a Foreign Key

I have one table: CREATE TABLE [dbo].[entry] ( [ID] [bigint] IDENTITY(1,1) NOT NULL, [EntryDate] [datetime] NOT NULL, [createddate] [datetime] NOT NULL, CONSTRAINT [PK_Entry_ID] ...
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0answers
77 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 ...
8
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2answers
158 views

Should I add transitive foreign keys?

Simple example: there is a table of customers. create table Customers ( id integer, constraint CustomersPK primary key (id) ) All the other data in the database should link to a Customer, so ...
7
votes
3answers
2k views

Foreign keys - link using surrogate or natural key?

Is there a best practice for whether a foreign key between tables should link to a natural key or a surrogate key? The only discussion I've really found (unless my google-fu is lacking) is Jack ...
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0answers
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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2answers
147 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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0answers
96 views

Same column relational Id to multiple tables

Is it appropriate to use a column as a relational id to multiple tables? For example: referenceId - int relational id to various tables tableReference - String defining the table This way I can ...
2
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1answer
520 views

size of a primary key and foreign key

Do a primary key and a foreign key referencing it must have the same column size in sql server 2008 ? could someone indicate me a link to a documentation explaining this ? Thank you for help.
2
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2answers
179 views

Should I drop a foreign key if I use a soft delete?

"ON UPDATE" scenario never happens in my application. As soft delete is used, "ON DELETE" cascade and restrict scenario never happen as well now. Then, should I just drop foreign key because I have ...
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1answer
320 views

MySQL InnoDB table accepts Non-Existent Foreign Key

Using EasyPHP 14.1 VC11 and phpMyAdmin (4.1.4) to create a website project in my home computer. The MySQL version is 5.6.15 according to the EasyPHP administration page. Working on Windows 7 64-bit. ...
3
votes
1answer
112 views

Many to many unique combination

So I originally thought I was going to have a one to many relationship in a database with the following tables ENTITY_JSON_MAP ATTRIBUTE_JSON_MAP Originally I was going to have an FK in ...
4
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2answers
282 views

How to write a query which finds all circular references when a table references itself? (II)

I have the following schema (names changed), which I cannot change: CREATE TABLE MyTable ( Id INT NOT NULL PRIMARY KEY, ParentId INT NOT NULL ); ALTER TABLE MyTable ADD FOREIGN KEY ...
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1answer
59 views

Schema design - Reference slightly different data in different tables

I'm trying to design a schema for a MySQL database and got stuck on the following. My database stores documents which should have relations with blocks of content. create table document ( `id` ...
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0answers
46 views

Problems with foreign keys in a mysql database

I am trying to link both these tables with a foreign key. But I keep getting error message "ERROR 1452: Cannot add or update a child row: a foreign key constraint fails " the foreign key is pwalk_id ...
1
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1answer
25 views

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 ...
2
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1answer
79 views

Conditionally join table

I'm new to database design and have designed a database that seems fine for the application but looks like it has a major red flag to me. I have a master table which is then joined to another table ...
2
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1answer
88 views

Can triggers be used to implement automated polymorphic association?

(Apologies for any bad formatting or ignorance of common practices within this community; this is my first question here.) I'm attempting to (re)design a MySQL database for a personal social ...
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1answer
169 views

Performance of checking for data in related tables

NB: this question is purely academic / to help improve my understanding of SQL Server performance. Given a master table which relates to one or more other tables, how would you determine the best ...
0
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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 ...
0
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1answer
77 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 ...
0
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1answer
37 views

Database relationship refresher

All, After several years of programming applications, I'm looking to refresh my understanding of databases. What I knew to begin with was fairly basic, and honestly, it's disappeared over time. I ...
0
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1answer
54 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 ...