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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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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256 views

Proper implementation of child (derived) table PK/FK during single and multiple inheritance hard coded generalization physical data model

Below is an image of hard coded generalization UML logical model of entities. I'd like to implement these classes as tables in a physical data model. Two derived classes/entities (Class2 and ...
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547 views

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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147 views

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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142 views

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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132 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 ...
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743 views

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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225 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 ...
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27 views

Cities and States (a few data): single table or splitted?

I am designing a DB schema and I need to store cities and states. I expect only a few rows, let's say, 20 cities. Example: id | city | state 1 | Rio de Janeiro | RJ 2 | Niteroi ...
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36 views

Many-to-many relationship, what's the best choice for primary key? [duplicate]

In advance, I'd like to apologize if it's a duplicate question... I can't find a direct answer, probably because I'm not a native english speaker. Straight to the subject: I have 2 tables: company, ...
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21 views

General Definition of/for Primary Key for Table with Repeated Entries (i.e., not in 1NF)

my first post, my apologies if this does not belong here, please refer me to the/a right site. So I am looking for a general form for a primary key given a table containing non-atomic repeated ...
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105 views

Sudden PRIMARY KEY violation on IDENTITY column

I have a log table with an ID identity column. Everything works fine for years; then, yesterday, I see the following error in the logs: The statement has been terminated. Violation of PRIMARY ...
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23 views

Can I use a Composite Key as criteria for selection in a query?

I have created a meeting minutes table and would like to use two fields as a unique ID for each meeting (field one is a meeting code (lookup from another table) for each type of meeting and field two ...
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75 views

How to use an RSA public key as the primary key to a table in postgres

I have a data set that needs to be looked up by RSA public keys. These keys are 392 text characters long. What is the best way to make that a primary and/or unique key? Should it be a BYTEA ...
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16 views

Table with composite unique cluserted key and non-clustered surrogate primary key [closed]

We are running a legacy application which is an OLTP SQL 2008 R2 database having all tables defined as heaps with non-clustered index on surrogate primary key. I am considering introducing ...
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68 views

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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40 views

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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151 views

Optimizing Queries HAVING COUNT and INSERT…ON DUPLICATE KEY UPDATE

There are two main queries I'm tying to improve, one question is much more conceptual and learning about databases and another is much more straightforward. Both cases deal with the same table It has ...
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71 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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324 views

choose Username or ID as primary key? [duplicate]

my sites dont need use ID at all, then I am trying to manage user by username. Assume my sites is abc.com, then access to user profile by URL: abc.com/user1 So if you want to view all info of that ...
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92 views

How to determine next value to use in composite key in SQL Server? [closed]

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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“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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195 views

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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911 views

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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8k views

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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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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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 ...
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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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3answers
48 views

Reset Key Names to Defaults?

I'm working with some tables/columns that were renamed at some point, but the names of the primary/foreign keys are still based on the previous names. In SSMS is there any (preferably automatic) way ...
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Can a surrogate key and a primary key be in the same table?

For example we have: Surrogate key: ABC123 Primary key: 1 Name: James Is this legit in a Data Warehouse table?
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Use surrogate or natural PK if a row is uniquely identified by two or more columns?

I am having a hard time choosing between natural and surrogate PK for my database table. The database is for a ranking system for an MOBA game. Here is more or less what I would do if I were to go ...
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302 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
25 views

Using default values in primary key

Good day. I have a table like this: CREATE TABLE mytable ( myname varchar(30), mydate date DEFAULT CURRENT_DATE, PRIMARY KEY(myname, mydate) ); EDIT: Forgot to mention I am using a ...
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2k views

Create relationship between two tables with composite primary key

I've created a table [t1] with two fields and a composite primary key, show in below: create table t1( id int, name nchar(10), primary key(id,name) ); I want to create a second table ...
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SqlServer: can one table's PK be the FK of other two table's? [duplicate]

I have three tables project, users and proj_user. The PK of proj_user table is the FK of project and users table's pk e.g.(project_id,user_id) My question is, is it possible for the project_id and ...
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1answer
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Batch converting indexes to keys [closed]

I have a legacy MS SQL Server database where all the primary and foreign keys were created as indexes. I am developing the new version of our software with Entity Frameworks, which I have learned ...
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Performance of primary key IDs with gaps (but in sequential order)

I know that having non-sequential IDs is bad for index performance. But assuming all my IDs are created in correct order, but with large gaps: i.e: 154300000 283700000 351300000 464200000 ...will ...
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3k 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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377 views

How SQLite index ID (or line number)

SQLite is based on a flatfile, and store virtual tables in a flatfile (I think based on offset, correct me if I'm wrong). But how it index the Primary Key (ID), which I think is identical to line ...
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35 views

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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2answers
3k views

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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3answers
480 views

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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1answer
50 views

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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177 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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294 views

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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1answer
42 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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1answer
34 views

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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3answers
341 views

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` ( ...