In relational database design, a primary key can uniquely identify each row in a table. A primary key comprises a single column or a set of columns.

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Basic SQL question about setting constraints

In code such as the following, what is the need to write constraint pk_dept primary key (deptno) if just simply primary key (deptno) works? Is pk_dept something the database uses internally, since it ...
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Update datatype of primary key without deleting the table-SQL Server [closed]

I have created a table State which my other table, Addresses references. CREATE TABLE State ( StateId varchar(20) PRIMARY KEY NOT NULL, Text varchar(40) NOT NULL ) I want to change its ...
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Can i have one foreign key to both parent and it's childs in postgresql?

I want to have a foreign key to reference table and it's children. Here's how I tried and failed: CREATE TABLE parent ( id serial, CONSTRAINT parent_pk PRIMARY KEY(id) ); CREATE TABLE child ( ...
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Postgres table contains 1 column, and that column is PK. How to insert new record?

In my application, I have an abstract base class, and 2 derived classes. The number of derived classed will probably not increase. If it does, it won't be more than a few. The class structure looks ...
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180 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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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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Use timestamp(or datetime) as part of primary key (or part of clustered index)

I use following query frequently: SELECT * FROM table WHERE Timestamp > [SomeTime] AND Timestamp < [SomeOtherTime] and publish = 1 and type = 2 order by Timestamp I would like to optimize ...
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Difference between surrogate key(s) and composite key(s)?

I'm a beginner with databases and have been perplexed by the various definitions to distinguish these two. Various google searches have not fully clarified their differences. Please help explain them ...
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55 views

InnoDB: SELECT COUNT(*) using primary key 25 times slower on Windows

MySql 5.6, InnoDB. I have a table with 8 million records. It has an integer primary key, and a unique index u1 CHAR(40). It also has a few small fields and a VARCHAR(1000). SELECT COUNT(*) FROM ...
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How should I handle unknown primary keys? [closed]

I'm working as a database-administrator at a school. Recently the school upgraded its pupil administrative software into a web-based solution. This works great, but this web-based solution is missing ...
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Autoincrement Primary Key For Constants

We are having an issue that is probably due to some poor design choice or lack of understanding of how to use primary keys. We have a simple constants table CREATE TABLE IF NOT EXISTS `constants` ( ...
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212 views

Relational database primary key requirements

I am trying to put together an ER Diagram to design a fairly simple asset tag tracking/inventory management system for our servers/switches/UPS/etc. The top-level entity corresponds to the business ...
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26 views

Which of tables key to reference?

MySQL. There is a table users with autoincrement primary key id. There is also a table employees (every employee is a user but not vice versa). The employees primary key is userid. The field userid ...
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526 views

MySQL non-sequential primary key of certain length

what's the best way to create a non-sequential primary key of a certain length in MySQL? I'm looking to use the primary key as a 'Pin' number which real actual human people can use to refer to the ...
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Primary key which is foreign key in an relationship is specified NOT NULL. Why?

I have question about a foreign key. Primary key which is foreign key in an relationship is specified NOT NULL in some book's example. Why? I was thinking that primary key couldn't take on value ...
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42 views

Don't know why MySQL is not creating table with primary key constraint [closed]

I can't understand why MySQL showing this error: #1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ...
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Check if a primary key value is referred in any other table

I am using oracle database. Is there a way I can check if the primary key value in one table is being used as a foreign key value (have any associations) in any other table? Example: if I have the ...
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Should I create a child table without primary key?

I'm designing a database with a child table that may contains billions of records in the future. So I try to use less fields (and smaller ones) as possible. So I'm considering not using a primary ...
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104 views

Derived classes with same base class and class specific ids

I have three classes in my project. One base class and two derived classes. public class Animal { public long Id { get; set; } public DateTime Created { get; set; } public string Name { ...
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Primary Keys for Adress tables

I'm working on a database that stores address information. Each address has a Street, Number, Bus (as in the apartment they live in) and CityCode parameter. The CityCode parameter is a FK to the City ...
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180 views

Is it redundant to set your primary key as a unique key?

I'm putting tables together in MySQL workbench and I'm currently ticking my primary keys to also be uniquely indexed. Is this a redundant configuration?
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Can we determine FDs if we are given some tuples?

I am taking a databases course and i'm learning about functional dependencies. I have searched around and did not find any information on this. My questions is if we are given a table with some ...
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Database design: Which will perform better, auto incremented column or a composite key for appointments

The schema of table is : appointment(date,time,patientID,...) pateint(patientID,PName,age,...) PS: two or more patient can came at the same time . The number of appointments per day up to 500 . ...
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Msg 2627 Violation of PRIMARY KEY constraint

trying to make a database for teams in a tv show here. but when I try and insert data into tblShowteam the following error made its appearance. Msg 2627, Level 14, State 1, Line 2 Violation of ...
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Can a complex primary key made up of 4 fields have only one of this fields set to AUTO INCREMENT?

I have a complex primary key, I wonder if what I write in the title is possible: I have a look up table with 4 fields (they should compose the primary key of the table): 1) an INT column; 2) ...
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217 views

Table design for departments with duplicate department numbers

How should I define a database table for my company's departments where we have a set of duplicate department numbers used by an upper management tier. dept_id dept_name manager_id ...
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136 views

How to arrange rows selected in MYSQL query?

I'm fetching data from a table "TABLE_A", it's having Primary Key as "PK_ONE" (which is unsigned INT) . I'm fetching data from "TABLE_A" with where clause on PK_ONE ; Ex: SELECT PK_ONE from TABLE_A ...
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457 views

Postgresql table with one integer column, sorted index, with duplicate primary key

I want to have a table in PostgreSQL with these properties: One column with an integer Allow duplicates in this column. Duplicates will be rare. Duplicates have no meaning logically and will be ...
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47 views

Modify legacy table schemas that have no primary key

I've been tasked with updating our database (SQL Server 2008) so that every table in it has a proper primary key defined. Due to various reasons over the years we have somehow built up some legacy ...
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How can primary keys in a Netezza table be indexed?

What is the best way to index a Netezza fact table with lots of primary keys. For now, let's suppose we have 10 primary keys. This table is mainly used to store meta data about our database. ...
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190 views

Impact of miss-ordered fields in a composite, clustered primary key?

I have tables where the primary key is something like this: -StoreID -BusinessDate Typically, there is one row for every store (~100) for every single day. One row for each store is inserted on a ...
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Two tables with the same primary keys

Can two tables have the same primary keys? For instance:
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Do I have to use Foreign key as part of composite primary key or not?

I'm designing a relational database. This is what I'm trying to design: I will have production orders and products. A production order will have one product, but a product could be on zero or more ...
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primary and foreign keys used in object-relational table

Currently I am designing an object-relational database based on an existing relational database with multiple primary and foreign keys, and was wondering if it is OK to use primary and foreign keys in ...
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unique BIGINT as foreign key instead of primary key in distributed system

I am creating user management database schema. I am using Postgresql as database. Following is my approach. Please suggest if there is any performance issue if I use this structure. Requirement: ...
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SQL Timeout when updating specific rows that goes away when other columns are updated

The data I'm going to provide won't be very complete, so I apologize in advance for that, and will happily supplement with more on request. I mostly just don't know where to begin looking, and don't ...
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1answer
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Phpmyadmin / mysql error defining primary keys as foreign keys of two separate tables

I am designing a mysql database using phpmyadmin 3.3.10.4. Everything in the database is InnoDB. I have two tables, person with primary key person.id_numberand e-mail_address with pk ...
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When should I create a primary key on multiple columns? [duplicate]

I'm interested to know in which case I should create a primary key on multiple columns and why ? To be more specific about my question, I want to know what are the advantages and disadvantages of ...
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Structure of an SQLite database for storing analytics with counters and hits

Before making this post, I referred to this and this which contain extremely complex solutions and hence, this question: I am building a spam filtering app that takes posts from a feed and deletes ...
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multi valued attribute as primary key

I am designing a database system for my current project and got this situation. I am having a functional dependency as D -> E Here D is multi valued attribute. D can be(i,j,k) or (i,j) or any ...
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Finding the closure and super keys of a schema?

I am working on a problem in which I have to look at the relation R with schema R(w, x, y, z), and the three functional dependencies: w -> z ; x,y -> w ;z -> y For every non-empty subset X of ...
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Should Primary Keys be arbitrary?

I have a lookup table PerformanceID (incremental integer - Primary Key - Identity Column) PerformanceRating (Integers from 1 to 5) Description (100 char description of what the rating means) ...
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Is there a way of implementing a composite primary key with varying fields in MongoDB?

Here is the information about my development environment: -Mongodb 3.0.0 -Microsoft Visual Studio Professional 2013 -.NET Framework 4.5 We are trying to design some MongoDB collections at work ...
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1answer
58 views

Is unique index combined with a “not null” constraint equivalent to a PK constraint?

I have these legacy table definitions (from here): CREATE TABLE [dbo].[JobItems] ( [ItemId] UNIQUEIDENTIFIER NOT NULL, -- lots of other columns CONSTRAINT [PrimaryKey_GUID_HERE] ...
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PostgreSQL 9.3: Minimize locking when updating a large table with primary key

I am building a DB solution to handle a fast stream of online events. Each event UPSERTs a row in a location_update table, using its car_id primary key. Since there are very few new car_ids, the ...
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45 views

SQLite table design for PK and/or UNIQUE

I'm trying to design a table in SQLite3, where I can perform these 2 actions. INSERT new row where a unique primary key is created. And INSERT new row with an given primary key Think of a ...
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Problems in Choosing Foreign Keys :S

I am designing my very first relational database. I am now in the conceptual design, building tables and views, selecting the primary and foreign keys and normalizing everything. But now, I am stock ...
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Part of composite foreign keys as primary key

I have a table A with a,b,c as primary key. Table B reference has a,b,c as foreign keys and it wants to set its own column d and foreign key a as primary key, Is it legal? Or does it have to set the ...
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Filesort when using view

I am sorry for asking, but I can't figure what i am doing wrong and filesort appears in my explain. The id column that I use for sorting in the following examples is a primary key... If I create ...
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108 views

For Postgres, how would I define a custom function to generate primary keys?

In postgres, primary keys are typically generated using a SEQUENCE. I am hoping to generate a unique random 12 character string for use as a primary key. How would I do this in Postgres?