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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Linking Fields From 2 Different Tables (Microsoft Access)

I am trying to link 2 fields from 2 different tables on Access but I will give an example to try and make the issue clearer. I have 1 table called "Employee Details" which contains the field ...
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Sybase ASA: Saving and dropping all foreign keys and most Primary Keys for (Bulk) Insert

Background Information: I am trying to migrate from an ASA 12 Database, to a ASA 12 Database by using a Remote Server. I have to migrate a lot of Rows (not all), spread over a lot of tables (not ...
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Can one part of a multi-column primary key be used across tables?

I want to use SQLite as file format for my app, a reporting program. Below is an idea of the kind of schema I'll use (just the first few tables). There will be one report per file and all tables are ...
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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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Returning auto-generated primary key after SQL insertion

I am trying to submit data to a database and then have it return the value of the user_id (primary key) created by the insertion, but I can't get it to return the value. I use the same query in ...
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persistence entity with composite key

I have class named 'User'. It has the following properties firstname lastname mobile email pin I want to design a table or hibernate entity that will have unique email for each row; the same for ...
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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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Storing URLs in a database

I am thinking about storing URL's in my database, but I am not sure whether the way I use is an efficient way to do things or not. Table name : url url_id (Primary Key & Auto Increment) url_value ...
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How to pass the value of PK to FK

Ok, so here it goes. I have a table called employee. then I have another table called languages. I need to copy the value of PK of employee table to foreign key in Languages table, rather than ...
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Speeding Up Query - Hangs at Sending Data - Indexed Correctly

I am looking for ways to speed up the below query. I currently have indices on FIRST, LAST, UNIT_PARENT, HomeAddressLine1, HomeAddressLine2, HomeCityNAme, HomeStateAbbreviation, HomeZipCode, HomeZip4, ...
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“Temporary file write failure” when trying to change primary key in MySQL

In MySQL, When I trying to change primary key by this query: ALTER TABLE `resources` DROP PRIMARY KEY, ADD PRIMARY KEY (`role_id`, `category_id`, `lang`, `model`, `rule`); I execute this query ...
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Crow Feet notation and identifying -vs- non-identifying relationships

Is it possible to distinguish between identifying and non-identifying relationships using the Crow Feet notation? Case in point: In table Book, part of the book's Primary Key is a FK to the Author ...
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Keys of a relation

I got relation: R = { (ABCDEF) , (A B F -> C, B C -> F, F -> A, F -> B, D E -> E, E -> D)} keys of this relation are: {BCE}, {EF} But i dont get it... why? Why not only {EF}.. it got less ...
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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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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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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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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?
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Creating mysql config setting per database

I am trying to setup MySQL so one database auto increments by 2. I am using the auto_increment_increment variable in my.cnf configuration file, but this is being applied to every database. I would ...
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50 views

Table with both primary key and unique key

My system requirement defines a unique business/domain/natural key (i.e. <yyyymmdd><branch_id><running_number>, in bigint). Should I use this unique key as primary key or I should ...
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Converting Entity Relation(ER) Model to Relational Schema?

I have the following ER Model I am trying to convert this to a relational database schema but I am not sure about several things: PORT_VISIT and PORT are weak entities. How do I figure on which ...
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Medical History - Is this DB properly design?

Could you please tell me if this DB is properly design? Are relationships type correct? Is there anything I should delete or add? Thanks you all very much!
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How can I make a foreign key from a fragment of the primary key?

I have this table: CREATE TABLE Phones ( Brand VARCHAR(20), Model VARCHAR(20), PRIMARY KEY (Brand, Model) ); A mobile phone can't be uniquely identified just by its model (for example: HTC (One) or ...
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redshift performance effect if use 32 character long unique string as Primary key instead of auto incremented int

In my analytics application I am creating 32 char long unique string for each hit as user_session. In current implementation, I am storing user_session in tbl_sesssion in session column and I am ...
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PostgreSQL replace primary key and converting non-serial to serial type

I'm basically building my own version of phpPgAdmin (if I get good enough to make it good enough I'll post it on a repository hosting service) and currently I'm revising my primary key tool to replace ...
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Using partitioned table, and dealing with auto_increment PK

I have a big table (>100 million rows) that tracks user's activities. It has an ID, which is PK and has auto_increment property. This is the only unique key. Table also has userid and datetime column. ...
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MySQL on Server side PRIMARY KEY taking automatically random Id

I have problem in my database which i have uploaded in Database Version libmysql 5.1.73 In that i got problem like one PRIMARY_KEY field incrementing random values. inserted id's like 1, 2, 35, 67, ...
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Setting the Relationship as a Continuous Line Without Changing the Qty INT into Primery Key on SQL

Now it is required to make the following database. In the following, if I tick the checkbox of "Identifying Relationship", the line will become continuous line but the key type will also be ...
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Auto increment holes in primary key - any issues?

I have an application that is creating large holes in the auto incremented primary surrogate key to the table as it uses lots of INSERT ... ON DUPLICATE KEY UPDATE queries. I'm looking into changing ...
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Impact of additional int field as primary key

Directly to the point, at one time I have a table like this: create table item( item_id varchar(50), constraint pk_item1 primary key (item_id) } However from my discussion one day, there is ...
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115 views

Overcoming the HDD IOPS limits on a billion row table? Is getting SSD the only solution?

I have a table with this structure: CREATE TABLE `requests` ( `userid` int(11) NOT NULL, `messageid` int(11) NOT NULL, `queueid` int(11) NOT NULL AUTO_INCREMENT, `problem_id` int(3) NOT NULL, ...
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Postgresql Retrieve / Find Primary Key Serial Autonumber field for Audit logs

I need to find the Primary Key field name in each of a number (approx 70) of tables to create audit logs. All the primary keys are type serial (auto incrementing integer) and all have the name in the ...