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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Unique insert performance: Primary Key vs Unique Index

I have a table of unique values (domains_unique), with collumn domain varchar(255), with more than 20 mil records. What's the fastest way to insert into the table, by keeping the domain unique ...
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1answer
500 views

SQL Server - storing ulong as primary key

I need to store ulong values as a primary key in SQL Server. Since SQL Server doesn't have a ulong datatype (or for that matter anything unsigned), the only way to go is to have column as ...
3
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1answer
478 views

Index Key Column Order

I have created a joining table for many-to-many relationship. The table only has 2 cols in it, ticketid and groupid typical data would be groupid ticketid 20 56 20 87 20 ...
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3answers
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Is a surrogate key better than a natural key in this case

I copied this code from here: CREATE TABLE records( email TEXT REFERENCES users(email), lat DECIMAL, lon DECIMAL, depth TEXT, upload_date TIMESTAMP, comment TEXT, PRIMARY ...
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220 views

Maintain table with too many insert

I have to create a table. Its size is going to increase very fast. Is there going to be any issue if many insert queries are fired at the same instant as mentioned here - User autoincrement ID for ...
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1answer
598 views

does last_insert_id() returns correct result when writes from multiple sessions?

I have a table in which there is a combination of 4 columns that will act as a unique key. Instead of using a composite primary key, I want to keep an id column as the primary key. This field is on ...
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1answer
129 views

Optimised Schema for City-to-City Distance Table

This is my first question, forgive me if this question is simple. I'm stuck here, trying to implement the relations for the data represented below. I want to scale it vertically (new rows), instead of ...
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5answers
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Sequential GUID or bigint for 'huge' database table PK

I know this type of question comes up a lot, but I've yet to read any compelling arguments to help me make this decision. Please bear with me! I have a huge database - it grows by about 10,000,000 ...
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2answers
196 views

How many fields is too much for a primary key?

I am creating a table to store information about the placement of objects in a grid (game map). For example, I have a 10x10 grid and I want to store, in the database, that cell (5,5) has a blue box, ...
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1answer
858 views

The four properties of a primary key

In our dbms class, these were the four properties of a primary key discussed for Oracle. Unique Not NULL Fully functional dependency Indexed I understand all the properties except the 3rd one ...
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1answer
103 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 ...
4
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2answers
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What happens to the index of a primary key after a DROP CONSTRAINT?

I am running PostgreSQL 9.1.4. I have a table with many existing rows, and a bunch of other tables with foreign keys pointing to it, for which I am trying to : 1 - Remove the pkey constraint on the ...
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1answer
536 views

How to alter primary key constraint for 2 columns in same table in SQL Server?

In SQL Server, I already created a table called tblDatabase with some columns. I want to add a primary key on the two columns DatabaseName and Servername. I tried to add: ALTER TABLE tblDatabase ...
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1answer
317 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 ...
7
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2answers
893 views

Should a log table get an id field or primary key?

I have a log table that captures the datetime stamp of when certain files were exported to another system. The exportedLog table currently has three fields: id (primary key) messageId ...
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1answer
734 views

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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1answer
149 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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1answer
3k views

What are performance benefits when using number type instead of using char/varchar?

From various posts, I have summarized about using number type instead of char/varchar for PK: If you choose char/varchar type for PK and your values are short (just some alpha numberic codes) then it ...
2
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2answers
420 views

Replacing composite key with surrogate

I have the following table that has a couple of million rows in it and is 99% fragmented virtually all of the time. My plan was to insert a IDENTITY field as a surrogate key to replace the current ...
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1answer
374 views

Surrogate key / Primary key: Better to use an existing unique data field or create a key field?

I am not sure if this question has been asked or not. At least I couldn't find it. I am curious about a primary key in terms of efficiency with data searching and retrieval. This is a hypothetical ...
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1answer
483 views

DynamoDB: searching with primary key or range key, which way is faster?

To those familiar with DynamoDB, I'm trying to make a table where items only have 2 entries. For example, . Most of the time I'll be searching the user_id with a facebook_id on hand. Amazon's ...
3
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1answer
381 views

How can I manage Primary Key length limit of 900 bytes when using hirarchyid 2 columns?

I have to define a Primary key on a table which has following 4 columns and its data types. GSiteID hirarchyid,, SiteID varchar(10), GComID hirarchyid, ComID nvarchar(10) As we know there is limit ...
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How do I create a rule for a Primary Key

I am using SQL Server 2005 and I need to create a primary key with an alpha character and 3 numbers together: p001 b201 I know I need to create a rule and bind that rule to the primary ...
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3answers
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Does the MySQL primary key affect the efficiency of a SELECT query?

Does the primary key serve any purposes apart from uniquely identifying a specific row? For example, a table with an autoincremented primary INT key could greatly aid in search due to the option of ...
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1answer
343 views

Using indexes to create multiple relationships to a table in order to enforce data integrity and add meaning

I'm working on an inventory database that uses supertype/subtype model. My question regards creating multiple relationships with the same tables using the primary key and composite indexes that also ...
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Primary key should be chosen so as attributes never change?

I was reading about keys in this DatabaseSystems book - The primary key should be chosen such that its attributes are never, or very rarely, changed. For instance, the address field of a person ...
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Why are runtimes different for a table including a primary key versus a table with a clustered unique index added after population [closed]

When I create a temporary table with a PK defined from the outset like this I get great performance in subsequent joins on that key: create table #temp ( field1 int not null field2 int ...
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1answer
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How does SQL Server choose an index key for a foreign key reference?

I am working with a legacy database that was imported from MS Access. There are about twenty tables with non-clustered, unique primary keys that were created during the MS Access > SQL Server upgrade. ...
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2answers
2k views

Postgres primary key sorted in the reverse order. Will it use the index efficiently?

My Rails database is backed by Postgres database. As you may know, each table in Rails gets assigned a primary key which is of Integer type and is indexed. My list views show records in the reverse ...
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2answers
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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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4answers
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Sort order specified in primary key, yet sorting is executed on SELECT

I'm storing sensor data in a table SensorValues. The table and primary key is as follows: CREATE TABLE [dbo].[SensorValues]( [DeviceId] [int] NOT NULL, [SensorId] [int] NOT NULL, [SensorValue] ...
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How should I save apache logs into a mysql table?

This is a php script to view apache logs. I want to save apache logs into a mysql database. Then add some rules for tagging urls using mysql REGEXP search, like: SET tag='some tag' WHERE url REGEXP ...
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Teradata: How to design table to be normalized with many foreign key columns?

I am designing a table in Teradata with about 30 columns. These columns are going to need to store several time-interval-style values such as Daily, Monthly, Weekly, etc. It is bad design to store ...
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2answers
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Index on primary key not used in simple join

I have the following table and index definitions: CREATE TABLE munkalap ( munkalap_id serial PRIMARY KEY, ... ); CREATE TABLE munkalap_lepes ( munkalap_lepes_id serial PRIMARY KEY, ...
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3answers
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Most efficient (or meaningful) way to index grid-based data

I have a MySQL table which I expect to be in surplus of a few million rows and 99% select statements. The problem I am having is coming up with a meaningful way to determine the Primary Key. (I have ...
9
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4answers
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Mysql int vs varchar as primary key (InnoDB Storage Engine?

I am build a web application (project management system) and I have been wondering about this when it come to performance. I have an Issues table an inside it there are 12 foreign keys linking to ...
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SQL - double column used from primary key with autoincrement

I am user the following as primary key in the SqlDB: I am doing the Index as Autoincrement, but it is autoincremented in general not per user. Example userid=1,index=1, then insert another for ...
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3answers
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Differences between “Unique Key” and “Primary Key”

What are the major differences between Unique Key and Primary Key in MySQL?
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Does the order of keys in compound Primary key make any difference?

Package Package ------- PackageID PackageName CityID PRIMARY KEY (PackageID) UNIQUE KEY (PackageName) FOREIGN KEY (CityID) REFERENCES City (CityID) Package versions: PackageVersion ...
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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 ...
0
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1answer
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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 ...
2
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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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1answer
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How is INDEX on Composite Primary Key in mysql?

When making a composite primary key for two or more columns, e.g. PRIMARY KEY(col1, col2, col3); will the system INDEX each column individually? The reason that I am asking this question is that when ...
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4answers
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Two-sided UNIQUE INDEX for two columns

Creating a table with composite PRIMARY KEY or using UNIQUE INDEX for two columns guarantee uniqueness of col1, col2. Is there a tricky approach to make the reverse order of two columns UNIQUE too ...
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2answers
172 views

Update primary key

I want to update a primary key column, but the change should cascade to all other child tables where this primary key is used as foreign key. Example: table1 has column "slug" as primary key. One row ...
4
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1answer
799 views

Primary Key Type's Effect on Performance in Oracle?

In MS SQL Server, it is well documented that the type of the primary key can have a dramatic effect on performance. Using narrower types and sequential values significantly improves insert performance ...
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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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updating mysql primary keys

I need to be able to swap values that are used in a primary key. Meaning, in one update statement, I need to change id 1 to id 2, and id 2 to id 1. In other relational databases, (Sql Server and ...
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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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Is it possible to change the data-type of a primary key column in SQL Azure? [duplicate]

Possible Duplicate: How can I alter an existing Primary Key on SQL Azure? OK, so say I have a table: 'Contact' and a primary key: 'ContactID'. The primary key is an INT but I want to ...