Tagged Questions

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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0answers
82 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 ...
2
votes
1answer
500 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
352 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 ...
2
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1answer
991 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 ...
0
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2answers
122 views

Multiple relationships between the same entities

Is there a name for when 2 entities can have multiple relationships between them?
0
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1answer
127 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 ...
2
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2answers
175 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 ...
0
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1answer
465 views

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 ...
0
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1answer
26 views

Good idea to include summary of frequently accessed data from another foreign-keyed table?

Sorry for poor title, I'll try to explain it in more detail here. I have an application that often gets a row from table A, then looks up a column from that in a foreign key mapping table (table B), ...
3
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2answers
154 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, ...
2
votes
3answers
363 views

Many to many link tables with history? [closed]

While creating a PostgreSQL database of customer subscribed services with DNS domains, I want to: enable customers to subscribe to multiple services each service can have multiple domain names per ...
0
votes
1answer
140 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) ) ...
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2answers
64 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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0answers
79 views

Need advice on this EER Diagram

This db will work with a CakePhp app and need advice about design. Is it good idea to put orders on center or should I put clients on center? Clients has orders and an order record can only have one ...
0
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1answer
133 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
1
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1answer
925 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. ...
0
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2answers
1k views

Delete rows in parent table based on criteria in child table - Oracle

I have a table B with a foreign key to table A. I want to DELETE some rows in table B, and I also want to DELETE their parent rows in table A. However, the delete criteria is based on table B. The ...
1
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2answers
139 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 ...
2
votes
2answers
1k 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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1answer
510 views

MySQL: update instead of delete if foreign key constraint?

I have a bit of a strange question. I know about insert on duplicate key update. My question is, is there something similar for deletes that fail because of foreign key constraints? For example: ...
4
votes
1answer
322 views

How to relate two rows in the same table

I have a table where the rows can be related to each other, and logically, the relationship goes both ways (basically, is directionless) between the two rows. (And if you're wondering, yes, this ...
2
votes
1answer
80 views

Is it necessary to drop foreign keys before adding a null column to a table and then re-add them?

I have generated some SQL Server(2008) upgrade scripts using SqlCompare. The primary objective is to add a null column. However, the generated script wants to drop foreign keys in a couple of other ...
0
votes
1answer
295 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 ...
1
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0answers
171 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 ...
1
vote
3answers
780 views

Replication fails because of a non-existent foreign key

I have been trying to get a previously working replication to start working. I have tried many settings, but I can't seem to make it work. Here is the scenario. I dropped all the FK constraints ...
1
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1answer
131 views

How to link a customer to a country when the city/state isn't known

We have a situation where medical systems are sold to hospital groups, but at the time of the order, we don't always know into which state and city the system will be installed. We always know the ...
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1answer
2k views

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. ...
1
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1answer
1k 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 ...
-2
votes
1answer
782 views

Cannot create FOREIGN KEY for a table [closed]

I'm not a professional DBA, I encountered a problem when I's attempting to create FOREIGN KEY for a specific table by the following SQL script (I'm using MySQL): ALTER TABLE mmy_answer ADD CONSTRAINT ...
1
vote
1answer
269 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 ...
5
votes
3answers
26k views

How do I insert a row which contains a foreign key?

Using PostgreSQL v9.1. I have the following tables: CREATE TABLE foo ( id BIGSERIAL NOT NULL UNIQUE PRIMARY KEY, type VARCHAR(60) NOT NULL UNIQUE ); CREATE TABLE bar ( id BIGSERIAL ...
0
votes
1answer
80 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 ...
1
vote
4answers
5k 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 ...
2
votes
2answers
982 views

Two primary keys to one foreign key

racing_couple ID (PRIMARY) breeding_couple ID (PRIMARY) egg IDpar(FOREIGN KEY) I have 2 IDs from 2 different tables (racing_couple and breeding_couple) and they are primary keys. In 3. table (egg) ...
-2
votes
1answer
185 views

How to represent it with UNIQUE indexes and foreign keys?

"Group" is a group of pupils. "Topic" is a topic of lessons. To every group corresponds exactly one topic. (So there may be multiple groups per topic.) To a pupil corresponds multiple groups, but ...
2
votes
1answer
1k views

prevent MySQL Workbench to add index for foreignkey constraint when it is first part of primary

I know for each foreign key we should make an index on its column, But it is not necessary when that column in first part of PRIMARY index. MySQL accepts this query: CREATE TABLE IF NOT EXISTS ...
1
vote
1answer
4k views

“Cannot add or update a child row” when deleting a record?

I have the two following tables: survey_main ---------- id name answers_main -------------- id survey_id I have the following foreign key constraint on the answers_main table: CONSTRAINT ...
13
votes
1answer
3k views

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

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 ...
11
votes
2answers
14k views

Good explanation of cascade (ON DELETE/UPDATE) behavior

I don't design schemas everyday, but when I do, I try to setup cascade updates/deletes correctly to make administration easier. I understand how cascades work, but I can never remember which table is ...
4
votes
2answers
2k views

Auto-increment key and Foreign Key as composite for relational database

I do not have any experience in databases other than what I have from just playing with workbench and trying to understand how I need to setup this database for a project. I have been searching the ...
2
votes
1answer
2k views

If foreign keys/cascade deletes are bad, why use a database-server with that feature?

I noticed wordpress/rails etc do not use foreign keys constraint or cascade deletes features from database. Instead they handle this in PHP/Ruby/scripting level! I have read this and this. Most ...
0
votes
1answer
589 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) ) ...
0
votes
1answer
670 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 ...
1
vote
1answer
1k views

Is it possible to force drop of mysql tables with FK?

For dropping a table in which a Foreign Key is used in other tables, it is necessary to drop all other tables having FK connection with the corresponding table. Is there a short way to drop a table, ...
2
votes
2answers
224 views

Performance effect of indexing foreign keys

My database is for an HR application with performance reviews and I am interested in whether I should index my foreign key. There are two tables involved. The first is a ratings table with 2 columns: ...
1
vote
2answers
168 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 ...
2
votes
1answer
3k views

Insert Row With Foreign Key Equal to ID - Circular Reference

In MySQL database I have an events table which has a circular reference to itself with the following columns. id (PK) | user_id (FK) | event_id (FK) | title Each new row inserted has a circular ...
0
votes
1answer
41 views

Table Design for user-specific and user-agnostic criteria

I want to design a table that is general enough to accommodate an increasing number of achievements as I come up with new accomplishments to reward. Initially, I thought to design the table as ...
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0answers
34 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 ...