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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“on duplicate key update” all the non-key fields mentioned in the insert

How can I update the field values mentioned in the insert portion without listing them again in the on duplicate key update portion? insert into tablename set keyname = 'keyvalue', fieldname = ...
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1answer
764 views

Question on Design for User + User Groups + User Types + Subscriptions Model

I am redeveloping an existing web application with both weak source code and a weak underlying database design. I'm trying to develop things in a way that future expansion will be much easier, ...
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1answer
545 views

Drop primary key without dropping an index

Is it possible to drop primary key constraint on a table without dropping the index? I have a situation when I want to remove the PRIMARY KEY to get rid of the NOT NULL constraints and set it to ...
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1answer
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What should one do if the auto increment primary key exceeds the maximum?

I have a primary key for a table with the following structure, **Field** **Type** nid int(10)unsigned I know the maximum limit of int(10) is 4294967295. But What ...
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2answers
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Is index_type ignored on MySQL primary keys in create table?

I have seen a create table whose primary key had an identifier where it should have an index_type, something like that: create table a (foo INTEGER, PRIMARY KEY foo_id (foo)); The thing is that ...
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1answer
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Oracle SQL 12c How to correctly use compound foreign keys in compound primary keys?

DISCLAIMER: I am a student. I do not work for an airline. I do not pretend to be a professional programmer. Greetings, I want understand what I need to correct in order for these tables to work ...
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3answers
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MySQL - Unable to Convert Primary Key to Auto Increment

I have a MySQL table where the Primary Key (int) was set by the software to be equal to the Primary Key (auto incremented) of the main table. Because of a change in design I now need the field to auto ...
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1answer
438 views

How to efficiently create a new PRIMARY KEY CLUSTERED definition online

Given a table with a PRIMARY KEY definition (acting as the clustered index), I want to efficiently change the definition of the PRIMARY KEY (or at a minimum, just the clustered index) online. I would ...
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Clustered index on a join table

Currently I have a table defined as follows, but I'm not sure what to cluster the table on: CREATE TABLE [Security].[UserGroups] ( [UserId] INT NOT NULL, [GroupId] INT NOT NULL, [IsAdmin] ...
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Superkeys of this relation

I am trying to find the superkeys of this relation, but I am having troubles finding out how many superkeys there are and exactly what they are. I figured out that the candidate keys were ...
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3answers
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Why does PK constraint require a separate index when I already have a suitable unique clustered index?

This is part of table definition from here: CREATE TABLE [dbo].[JobItems] ( [ItemId] UNIQUEIDENTIFIER NOT NULL, -- lots of other columns CONSTRAINT [PrimaryKey_GUID_HERE] PRIMARY KEY ...
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4answers
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NVARCHAR column as PRIMARY KEY or as UNIQUE column

I'm developing a SQL Server 2012 database and I have a doubt about nvarchar columns as primary keys. I have this table: CREATE TABLE [dbo].[CODES] ( [ID_CODE] [bigint] IDENTITY(1,1) NOT NULL, ...
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3answers
777 views

File name as primary key?

I have a few tables I'm going to create for a website, Literature, video, and image. Is there a good reason why I shouldn't use the file name as a primary key. For instance... "someimage.png" as the ...
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2answers
702 views

Generalisation in databases

I am working on a Hospital Management project in DB2. I have one table for staff with a primary key of staff_id. The hospital has to have different staff... e.g doctors,nurses,e.t.c. Is it better to ...
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2answers
442 views

Can different tables have columns with the same name if those columns are not primary keys? [closed]

I know it's a simple enough question but my textbook is very confusing about it.
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Primary key auto increment best practices

Apologies if something similar has already been asked, I wasn't sure of the best term to search for to get what I was after, so please let me know if there is already a bunch of other related ...
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2answers
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IDENTITY_INSERT is set to OFF?

Here is my script of my db , CREATE TABLE [dbo].[MyTable]( [ID] [int] IDENTITY(1,1) NOT NULL, [Code] [nvarchar](25) NULL, [Name] [nvarchar](25) NULL, [dob] [date] NULL , CONSTRAINT [PK_MyTable] ...
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1answer
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Is it require to fill all tables inside of the database?

Now,I created upper that table and in order to test I will give 3 textboxes values as below. SqlCommand cmd = new SqlCommand ("Insert Into dbo.PrnInf(PrnName, PrnSurName, PrnEgn ) Values ...
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1answer
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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.
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1answer
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postgresql bigserial or sequence using jpa

I'm a java developer working with jpa, before to define the indexes in my entities i would like to known which one is faster o better to use?.
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3answers
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Platform independent select ordered by primary key

Is there a reasonably standard way to perform a select on a single table and have the result set ordered by primary key without having to specify the primary key condition explicitly? Ideally I wish ...
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2answers
557 views

What is the advantage of using numeric primary keys in a relational database?

Many tables in a relational database system (in my admittedly limited experience) have this sort of structure (Oracle syntax as that's what I'm used to): create table widgets ( widget_id number ...
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1answer
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What's better here - a single column or multicolumn primary key?

Let's assume you have a table groups and a table item. Each item belongs to exactly one group. It is an inherent part of that group. An item cannot exist outside of a group and it cannot be moved to ...
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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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2answers
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Should I replace my varchar primary key with an integer primary key?

I have a table that has a varchar primary key that's associated with "Base Product Codes". They rarely change, and if they do, it's usually just being deleted or added. I figured it would be better ...
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Why would i get a duplicate write error of auto-generated primary key?

Hi I'm not a DBA so forgive my ignorance. I don't have access to administrator tools etc. However, I do know that we have a live server which is approaching capacity ie 80%-90% full perhaps. What is ...
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1answer
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Can I use a Clob as a table key (from Java)?

Following a suggestion made to another question to store large amounts of text: can one use a CLOB as primary key field (i.e., from Java's DataNucleus implementation of JDO)? I know it is probably a ...
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2answers
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Single Identity column and composite key, which to make primary?

I've got a table that's a working copy subset of a base table. The base table has a composite key with a clustered index. However I need a single column unique identifier for my framework to work ...
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2answers
158 views

Does a composite primary key break the first normal form?

Does having a composite/compound key (using multiple columns/attributes) to form the primary key break first normal form? (I am assuming that this is handled by the DBMS, and so the attribute ...
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2answers
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Does my table need a primary key and clustered index change?

I have a table holding 1.7 Milion rows. Definition: CREATE TABLE T( [ID] [uniqueidentifier] NOT NULL, [AID] [uniqueidentifier] NOT NULL, [BID] [uniqueidentifier] NOT NULL, [iType] [int] NOT NULL, ...
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2answers
750 views

DynamoDB - Multiple range keys

Is it possible to have multiple fields as range key? Say I have a table where each row is uniquely identified by <A,B,C> ------------------------------- A | B | C | D | E | ...
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1answer
202 views

Why does MySQL increment the auto_increment value when there's a constraint violation?

I have a table in a MySQL database with one column id, which has auto_increment and the Primary Key. There's also a Unique constraint in this table, on different columns. I noticed that when I try to ...
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1answer
154 views

Primary Key Question

Building a database on Access 2007 and having trouble selecting the primary key. The tables consists of a student table and another table where the students are checked in. I would have liked to make ...
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best approach to keys, if data from separate DBs to be presented in same UI

Suppose we are creating databases containing information about monkeys, and a user interface to present monkey information to users. We have two separate databases. The schemas are identical (and are ...
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1answer
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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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1answer
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Missing PK/FK after database migration

We recently had a server migration. A new server is now the PROD server, and what used to be the PROD server is now the staging environment. Apparently, the data was transferred correctly, but the ...
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3answers
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performance of multi field primary key or 'contrived' 'semi artificial' key

This is not a question regarding the benefits or otherwise of using an artificial auto increment key in any given table against using a multi-field 'primary key'. That discussion (or argument) can ...
2
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1answer
50 views

Surrogate vs composite key in hierarchical data structure

I'm currently evaluating a schema for a hierarchical data structure. My main problem is how I should design the schema to prevent inconsistent data (reference of foreign key in another hierarchy). The ...
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1answer
153 views

Oracle: How to create a “reverse” index primary key?

I can create a primary key for a table and then reverse it with the command alter index T_PK rebuild reverse online; How can I create it reversed?
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1answer
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Foreign Keys to tables where primary key is not clustered index

I'm focusing on SQL Server here, but I think this is a database agnostic question, really. I have a table whereby a Guid is logically the primary key. However, uniqueidentifiers apparently make ...
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1answer
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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 ...
2
votes
1answer
287 views

Almost sequential GUIDs vs random GUIDs?

I'm looking at using GUIDs (UUID) as primary key with clustered index in SQL Server. In my webb-app I have many clients who will create items client side in javascript and save them only now and ...
2
votes
2answers
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Relations, dependencies and normal form

I have some issues in understanding about relations and dependencies. I will show two examples and what I want to know: Assume the relation GTX {G,T,X} with the following dependencies: G,X -> T ...
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1answer
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Does the size of the primary key contribute to table size?

I have a table (InnoDB) with data length around 36G and index length 23G. It had a composite primary key across three columns. As an initial attempt to reduce the size of this table, I dropped the ...
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1answer
294 views

Validate Primary Key and Index Selection

I have a table that will store transaction data from store sales registers, I have read quite a bit on index and key choice and below is what I have concluded is the best option but I am new to this ...
2
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1answer
55 views

Two tables with the same primary keys

Can two tables have the same primary keys? For instance:
2
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1answer
37 views

Should I create many ID for a same Person/entity in my DB?

In my model, I must store the name of the teacher of some kids and the classroom in which the teachers work, let’s say. All of the hundreds of teachers in the schools have 1 and only 1 classroom, ...
2
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1answer
140 views

If A and B are candidate keys, then AB is candidate key or not ?

If R{abc} is a relation, f{ a->b b->a a->c b->c }, then a and b are candidate keys. What about ab ? Is it a candidate key or is it a super key or both ?
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2answers
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Is there a good way to select a row where the key represents the lower bound of a range?

I am designing some tables and a number of the tables have as the key a lower and upper bound which never overlap. I want to query by a value that can fall withing any of those ranges. If I keep both ...
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2answers
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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) ...