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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Is it recommended to use Identity as an alternative to primary key?

We can declare an Identity like id_num so that id_num will have an increment of unique numbers. CREATE TABLE new_employees ( id_num int IDENTITY(1,1), fname varchar (20), minit char(1), lname ...
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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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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 ...
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What could cause an auto increment primary key to skip numbers?

I have a table created with the following T-SQL: CREATE TABLE [dbo].[TableName]( [id] [int] IDENTITY(1,1) NOT NULL PRIMARY KEY CLUSTERED ( [id] ASC )WITH (PAD_INDEX = OFF, ...
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780 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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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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What Columns to create Indexes on?

I have a table , which contains upto 20 columns. The data is selected, inserted, and deleted by 3 columns: Username, StartDate, and EndDate. These 3 columns are NOT unique. The table is a ...
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does the mere existence of a primary key increase query speed for large data sets?

So, I have a table with about 2.4M rows and ~30 columns. There is no unique column within the data. The data is transaction logs from stores where each transaction number is only unique on a per store ...
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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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When do you add your foreign keys?

I'm scripting out a fairly simple database so I can simply hand off a script to someone else for an application to use. I'm curious about where best practice/the community stand on this: When should ...
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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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How are auto_increment keys handled in INSERT (SELECT * FROM…)

I have table1 and table2 in MySQL. Both have a primary auto_increment key id. If the table schemas match and I do INSERT INTO table1 (SELECT * FROM table2) what happens with regards to the new rows ...
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Auto Increment Primary ID inserting random values

Today I was asked to look into this problem and I have never seen anything like this before. A table in our MySQL database, with a primary IDs column, which is set to autoincrement int, had some weird ...
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Multiple primary keys

I am new to database design and have been looking at some example data models here. One thing I don't understand is if you have a table like client_addresses from the link above: ...
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serial field issue

Q: I use a serial as a datatype for my primary keys in my tables. I insert a lot of data then truncate these data one after one many times to test the data entry. My question is: Is there any ...
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“Transitive” keys

I have a central table, A, which will have a key that I'll call A_ID. Now, I have a table B in a "one to many" relationship with A (many B's map to one A). Each link will, of course, have a link ...
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Relationship with a table without unique/primary key

I have a database with 3 tables. Table Work, with a field named workName. Table SubWorks, which have a field subWorkName and work with a relationship with Work.workName. And table Activity with ...
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Multiple primary keys in PostgreSQL

I have the following table: CREATE TABLE word( word CHARACTER VARYING NOT NULL, id BIGINT NOT NULL, repeat INTEGER NOT NULL ); ALTER TABLE public.word OWNER TO postgres; ALTER TABLE ONLY word ADD ...
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How do I validate all my constraints in postgresql?

It seems like I have been bitten by the first bug described in the release notes of postgresql 9.3.4: http://www.postgresql.org/docs/devel/static/release-9-3-4.html I now have e.g. duplicate primary ...
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Column suitable for natural key?

I have read many articles now about natural vs surrogate primary keys, and came to the conclusion there is no single best practice. I have a table that will have around 2000 definite unique values, ...
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MySQL, temporary on disk table on primary key retrieval?

MySQL 5.5.24, Windows 7 64-bit. I've InnoDB table with primary key defined on three columns: CREATE TABLE `common_descriptions` ( `object_id` mediumint(8) unsigned NOT NULL DEFAULT '0', ...
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MySQL looking up more rows than needed (indexing issue)

In our MySQL 5.5 database, we have following InnoDB table with 30M+ rows: +----------------+-------------+-----------------+--------+ | participant_id | question_id | given_answer_id | status | ...
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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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Is there a way to extract a report of or script all of the primary keys in a database?

I have just discovered that deployed copies of one of our databases have no primary keys. This is probably the fault of the SSMS Import/Export wizard, which has done the same to me. Our master copy of ...
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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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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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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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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 ...
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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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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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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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198 views

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 ...
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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 ...
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compound primary key with separate id field for reference

I am trying to build locations into a database like so: Country -> Region -> Town Countries will be populated with a list of pre-defined worldwide countries, regions & towns are input by users. ...
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one to one relationship

This is my database structure: Users {user_id, username} Profiles {profile_id, user_id, user_views} My question is: If I do it the way mentioned above, should I to set user_id as primary key or ...
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MySQL auto_increment delivers different primary key in MyISAM and InnoDB

I have a table with auto incremental primary key. If I want to change a row and add new rows I got different primary keys depending on engine MyISAM and InnoDB. The original table is: pk.. ...
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Would Mongo's ObjectID work well in InnoDB's clustered index?

Mongo's ObjectID is defined like this: ObjectId is a 12-byte BSON type, constructed using: a 4-byte value representing the seconds since the Unix epoch, a 3-byte machine identifier, ...
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Key lookup partition pruning

I have a query inner joining multiple tables all of which are partitioned and have 10 partitions each: SELECT A.COL1, B.COL2, C.COL3 FROM A INNER JOIN B ON A.ID = B.ID INNER JOIN C ON A.ID = C.ID ...
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Is there a tuning parameter for MySQL that allows you to set an on-disk gap between non-sequential primary keys?

I understand that one of the primary issues with using a non-sequential primary key is that every disk/memory write that does not come after the last known key causes a re-write of everything from the ...
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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 ...
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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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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 ...
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How to determine next value to use in composite key in SQL Server?

I am trying to figure out how to determine the next value to use when adding a new record to a table that uses a composite/compound primary key in a system with concurrent users. Suppose I have an ...
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Primary Key choice on table with unique identifier

I'm reconsidering my choice of Primary Key on a table, and would like some input. Some context: We are building a REST API, where clients access "Assets" identified by a GUID. So, the table for ...
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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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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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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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MySQL Subquery returns more than one row

I have a table namely tbl_plays. It has the following columns and data id(PK)| gameid | drawid | etc ---------------------------------------------- 1 | 1509 | 73 | ...
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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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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 ...