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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MySQL - Database Design : Encrypting user id and creating a mask for further internal references

For a food order delivery system that I am working on, I want to make sure my user's private information is well protected; from system admins too. So I thought of coming up with this concept of ...
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Why only one candidate can be the primary key? [duplicate]

I'm a rookie to DBMS. I have read that only one candidate key can be the primary key. Why not more than one ? Please explain with an example.
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27 views

Can I rely purely on an auto-generated unique primary key for CRUD? [on hold]

I am in the process of developing a large web-based application that uses a SQL server database for data storage. There will be multiple accounts all sharing one database for generic account related ...
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30 views

Converting a composite primary key to composite unique, and adding an auto-incremented PK column

Background I have taken over responsibility for a table that, in the long run, will grow monolithic. The table is a very simple link table with 2 columns, call them col1 and col2, both being foreign ...
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3answers
238 views

Should I add an auto-increment / IDENTITY field to a cross-reference table just for PK purposes?

I'm adding the following cross-reference table to my SQL Server-hosted DB: company_id bigint not null (FK) org_path nvarchar (2048) not null The company_id field refers to the id field in another ...
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47 views

What are the general practices considered to constitute a good user id? [closed]

I could not settle on a good pattern to generate my user ids for an upcoming project that could scale up in a few months. The project is about ordering food online and I need to store user ids and ...
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0answers
23 views

mysql duplicate key error during restoration through mysqldump data

I have a mysql database which is having one table for geo location and saves latitude and longitude values of users. The fields are as followed CREATE TABLE `USER_LOCATION` ( `LATITUDE` float NOT ...
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1answer
26 views

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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1answer
55 views

Two tables with the same primary keys

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

Decomposition In Boyce-Codd Normal Form may lost relations?

Let be the following Realtion R={UtilisateurID, Nom, Prenom, AdresseEmail, Login, Passwd, ServeurMail} with the functional dependencies: F = { UtilisateurID → Nom, Prenom UtilisateurID, ...
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1answer
45 views

InnoDB: secondary key that's 'parallel' to primary--do joins wherein the resulting primary keys are contiguous perform better?

Say I have a table ( person_id INT AUTO_INCREMENT, birthday_timestamp BIGINT, country, state, ..., PRIMARY KEY (person_id), KEY (birthday_timestamp) ) where people are added the instant ...
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1answer
45 views

Foreign key as part of composite primary key or not?

I'm designing a relational database. This is what I'm trying to design: I will have production orders and products. A production order will have one product, but a product could be on zero or more ...
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1answer
55 views

Automatic index creation for primary vs. foreign keys in Postgresql

For PostgreSQL 9.4 (http://www.postgresql.org/docs/9.4/static/ddl-constraints.html) it is stated that A foreign key must reference columns that either are a primary key or form a unique ...
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0answers
21 views

Varchar PrimaryKey. Clustered or nonclustered? [duplicate]

I am working on a legacy database. The primary key is clustered varchar(128) and the table contains a high volume of data. Does it necessarily help performance if I change the clustered PK to ...
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1answer
21 views

Difference between surrogate key(s) and composite key(s)?

I'm a beginner with databases and have been perplexed by the various definitions to distinguish these two. Various google searches have not fully clarified their differences. Please help explain them ...
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3answers
112 views

What does having the primary key as the last column in a composite secondary index in an InnoDB table do?

Say I have a 1-to-N relationship (person_id, pet_id). I have a table where pet_id is the primary key. I understand that an InnoDB secondary index is essentially a B-tree where the values are the ...
3
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1answer
596 views

Is SYSUTCDATETIME a safe primary key?

I have a serially modified table of processed events. A utc time for when it was processed and an eventId. Is it safe to use SYSUTCDATETIME() as my primary key? I can easily use a surrogate key but ...
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1answer
24 views

Primary key which is foreign key in an relationship is specified NOT NULL. Why?

I have question about a foreign key. Primary key which is foreign key in an relationship is specified NOT NULL in some book's example. Why? I was thinking that primary key couldn't take on value ...
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1answer
50 views

Don't know why MySQL is not creating table with primary key constraint [closed]

I can't understand why MySQL showing this error: #1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ...
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1answer
72 views

How can I randomize primary key values?

I need to avoid having my primary keys sequential. Basically looking for this in MySQL: https://wiki.postgresql.org/wiki/Pseudo_encrypt
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38 views

primary and foreign keys used in object-relational table

Currently I am designing an object-relational database based on an existing relational database with multiple primary and foreign keys, and was wondering if it is OK to use primary and foreign keys in ...
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27 views

unique BIGINT as foreign key instead of primary key in distributed system

I am creating user management database schema. I am using Postgresql as database. Following is my approach. Please suggest if there is any performance issue if I use this structure. Requirement: ...
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1answer
65 views

Add a primary key constraint to an existing unique column

I've seen lots of information around adding a new primary key column to a large database table, but I have a somewhat different situation. I have a large table (~90,000,000 records), that has no ...
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1answer
53 views

SQL Server Management Studio: The columns in table do not match an existing primary key or unique constraint

I have two tables: Students and Courses. I want to set a foreign key in the Students table from the couseId column to the courseId column in the Courses table. I have set primary keys to both ...
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67 views

SQL Timeout when updating specific rows that goes away when other columns are updated

The data I'm going to provide won't be very complete, so I apologize in advance for that, and will happily supplement with more on request. I mostly just don't know where to begin looking, and don't ...
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565 views

Add autoincrement to existing PK

I created a table in a DB that already exists in another DB. It was initially populated with the old DB data. The table's PK had to receive the values that already exist on those records, so it ...
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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
63 views

Phpmyadmin / mysql error defining primary keys as foreign keys of two separate tables

I am designing a mysql database using phpmyadmin 3.3.10.4. Everything in the database is InnoDB. I have two tables, person with primary key person.id_numberand e-mail_address with pk ...
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1answer
30 views

Find insert/update/delete queries that reference a partitioned view

I have just given a SQL Server with performance problems. The database is very large and use distributed views with a very large primary clustered key. (24 bytes). I would like to change this primary ...
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2answers
441 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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1answer
33 views

Trying to understand how an auto increment primary key is better than no primary key and some other primary key questions

I am trying to understand primary keys better, how to use them effectively in table design and in queries. First, are the primary keys themselves used in WHERE clauses? For example, if I have a table ...
2
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1answer
60 views

Primary key addition for a table which contatins no data is too slow

We are using mysql. We are running 10 alter queries which contains 3 Primary key deletion and 4 column addition and 3 primary key addition. And this alter query is on three tables which don't contain ...
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35 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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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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1answer
116 views

Unique identifier field with a conditional

I have a database that's not in production, so the main table being CustodyDetails, this table has a ID int IDENTITY(1,1) PRIMARY KEY column and I'm looking for a way of adding another unique ...
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1answer
116 views

Update multiple Ids when SET = (Sql Query)

I want to update multiple records however the value being set is based on the primary key of the given record. This is not an issue with a single record as I can use: UPDATE T1 SET A1 = (SELECT ...
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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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1answer
43 views

Chance of duplicate on single select max into statement

Against my will, I am told to use the following method to generate a new pk value. INSERT INTO SERVER_MONITERING(SM_SEQ, CPU_USE, MEMORY_BASE, MEMORY_USE, DISK_BASE, DISK_USE, ...
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2answers
109 views

Check if a primary key value is referred in any other table

I am using oracle database. Is there a way I can check if the primary key value in one table is being used as a foreign key value (have any associations) in any other table? Example: if I have the ...
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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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292 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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Should I create a child table without primary key?

I'm designing a database with a child table that may contains billions of records in the future. So I try to use less fields (and smaller ones) as possible. So I'm considering not using a primary ...
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3answers
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Programmatically finding minimum set of fields necessary to create a unique composite key

I am importing flat files from different sources into tables in SQL Server. I am creating a composite primary key using a combination of fields from the extracts that will give me a unique key for ...
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2answers
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What could justify a non explicit - non atomic primary key

I'm working as a "guest" dev at a random company. I'm working with a table that does not have a primary key by definition(Oracle). The column named "SOMETHING_ID" is varchar2(10) and constructed at ...
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37 views

When should I create a primary key on multiple columns? [duplicate]

I'm interested to know in which case I should create a primary key on multiple columns and why ? To be more specific about my question, I want to know what are the advantages and disadvantages of ...
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29 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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Structure of an SQLite database for storing analytics with counters and hits

Before making this post, I referred to this and this which contain extremely complex solutions and hence, this question: I am building a spam filtering app that takes posts from a feed and deletes ...
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What is the best approach to find all fields that has (Foreign Key and Primary Key) constraints in a Mysql database?

I have a mysql database that has 250 tables. I would like to run a query to retrieve: tableName ; FieldName ; ConstaintName (Primary or foreign key). I could use ...
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76 views

multi valued attribute as primary key

I am designing a database system for my current project and got this situation. I am having a functional dependency as D -> E Here D is multi valued attribute. D can be(i,j,k) or (i,j) or any ...
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119 views

Derived classes with same base class and class specific ids

I have three classes in my project. One base class and two derived classes. public class Animal { public long Id { get; set; } public DateTime Created { get; set; } public string Name { ...