Questions tagged [database-design]

The development of the conceptual schema and/or the logical model and/or the physical settings of a database.

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How to remove data redundancy in product table if multiple suppliers are there for same product

I am designing a database where I have different products and suppliers. For example, I have a product, "mobile phone", say an Apple 5S. This will be sold through my website from different ...
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1answer
1k views

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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3answers
587 views

SQL How to Convert Single Tenant Databases to a Multitenant Database

We have a legacy application. For some reason, someone decided to create a database for each customer. So we have 500+ databases with the same schema. I would like to convert into One multi-client ...
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3answers
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Copy table with separate sequences for serial columns

While creating a column management tool I came across the need to quickly replicate tables in PostgreSQL so I would not test new tools with non-test tables. To effectively test the new column tool ...
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2answers
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help in multi-language medical database?

My project is to design a medical database for many countries. This database contains many parts: medicines, medical centers, patients, etc. for every country with its own language. I started my ...
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1answer
131 views

How to store a version sequence per product

I need to create a table like the following one: +----+---------+---------+ | Id | Product | Version | +----+---------+---------+ | 1 | 1 | 1 | | 2 | 1 | 2 | | 3 | 2 |...
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2answers
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INT or CHAR for a Type Field

What is the best design for a table, a Type field that is of int or char(1)? In other words, given this schema: create table Car ( Name varchar(100) not null, Description varchar(100) not ...
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1answer
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Does creating a unique constraint on a Postgres column remove the need to index it?

Does creating a unique constraint on a Postgres column remove the need to index it? I expect that an index is automatically needed to maintain the constraint efficiently.
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2answers
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Find parent rows that have identical sets of child rows

Suppose I have a structure like this: Recipes table RecipeID Name Description RecipeIngredients table RecipeID IngredientID Quantity UOM The key on RecipeIngredients is (RecipeID, IngredientID). ...
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2answers
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How to implement soft deletes?

What is your method of implementing soft deletes in a database? Ideally the solution would allow for decent performance on large tables take relationships into account take unique keys into account ...
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3answers
28k views

Database design to track student attendance

I was having a doubt regarding the design of a database table to track students' attendance. Currently, my table students have atleast 4000 students. Creating a database for attendance to track their ...
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1answer
2k views

Designing a database structure for companies and stock owners

I'm working on a personal project where I want to make a database that holds the information for every owner of every public company. Say for example "Sears INC" and the program would get the ...
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2answers
255 views

Is there some drawback to define SPARSE columns?

I have a table which has a lot of NULL values in columns. But some columns don't contain NULLs at all (although nullable). Is there some drawback to declare all of these columns as SPARSE?
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1answer
998 views

For alignment optimized table is bigger than original table - why?

In another question I learned that I should optimize the layout from one of my tables to save space and have better performance. I did this, but ended up with a larger table than before and ...
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2answers
353 views

When to add another lookup table for the same field

Example Table Recipe uses a lookup table for Recipe Category; Table Ingredient uses a lookup table for Ingredient Category; They are in a Many-to-Many relationship; A Recipe Category will not be used ...
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6answers
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Database design for an exam

I am designing database for an exam, and I am stuck. I do not know how to do it. Here is the relevant information: Student answers 10 questions. Each question has 3 options (answers) and student ...
4
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1answer
11k views

Is it “OK” to have a table that only contain foreign keys?

By "OK", I mean "it doesn't have any bad impact with the overall database design". For example, will it cause insertion problems? Or will it be a problem in the future when I add field in the table?...
4
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1answer
475 views

Proper Database Partitioning

I had asked a previous question "Proper technique for storing users event data" and the correct answer in my opinion was to create a database partition. Now from what I have read on it there are ...
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3answers
2k views

Best way to model a single user with multiple usernames

I'm looking to write a website where a user will login with their email address and password, but can have multiple usernames. The context is a social gaming website. This may result in a user ...
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2answers
571 views

Should I create multiple tables for different task states?

I have a tasks table in my database and, in the business domain of interest, tasks can have multiple states: open, begun, in review, completed. Despite having open and begun in the same table, ...
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1answer
2k views

How to normalize my db schema for a quiz application? [duplicate]

I am putting together a quiz application. (I'm calling each quiz a "challenge") I have a "challenge" table and a "challenge_question" table which is pretty straightforward. challenge table: id ...
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1answer
1k views

Multi-tenant database

We are building a database for a SaaS web application. We have been told to use a multi-tenant approach and to expect over 100,000 tenants to be using the system over the next 5 years, so we're ...
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1answer
1k views

Data Model for Online Examination - Matching Questions

I'm designing a module for a client that allows them to administer certification examinations via their website to seminar attendees. I'm stuck on how to store the data for matching questions and ...
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1answer
12k views

Set permissions on all objects for SQL users

I have a procedure that loops through all objects in the database and assigns them proper permissions to that object. I want to know if there is a better way to do this? I use a model database to ...
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1answer
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Pros and Cons of having additional columns in join table of many to many relationship

I searched but did not find any discussions on this topic. Are there any pros and cons on creating many extra columns on joined table? Does it affect speed of data retrieval because we are joining 3 ...
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3answers
763 views

Heterogeneous ordered list of value

I have the following object model: class A { List<Thing> orderedListOfThings; } interface Thing { } class X implements Thing { int attr; } class Y implements Thing { String ...
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1answer
4k views

Db design for a quiz with variable number of answer choices, and each worth different score in a different category?

I'm working on a question/answer project and having a hard time coming up with a suitable database structure. Each question can have from 1 - "n" answers, and each answer is associated with one of ...
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2answers
2k views

Database for efficient range aggregate queries?

As a simplified example, suppose I have a table like this: seq | value ----+------ 102 | 11954 211 | 43292 278 | 19222 499 | 3843 The table may contain hundreds of millions of records, and I need ...
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1answer
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What's difference between standard view and indexed view in SQL Server [closed]

I learn that the indexed view holds the data from base tables while standard view does not holds data.Is it means that the indexed view need memory and standard view don't? Indexed view needs to be ...
5
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2answers
1k views

Best fill factor for GUID clustering key

We have a database that uses GUIDs for most of their columns in a data (non sequential). Does anyone have any best recommendations for fill factors on a GUID database in an hgih insert/update database?...
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2answers
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Maintaining referential integrity in a booking system

I am developing a second version of a corporate training booking system on Microsoft SQL Server 2005. I have 3 tables (simplified for this question). Table 1- CourseSize table- this determines the ...
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2answers
3k views

Constraint many to many table between two child tables

New to this exchange site so I hope my question isn't inappropriate. Creating a somewhat normalized database I had one design problem I'm not sure how to handle efficiently. One table has a One-To-...
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1answer
7k views

Two-column foreign key constraint only when third column is NOT NULL

Given the following tables: CREATE TABLE verified_name ( id SERIAL PRIMARY KEY, name TEXT NOT NULL, email TEXT NOT NULL, UNIQUE (name, email) ); CREATE ...
4
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1answer
185 views

Checking existence and syncing data with millions of rows

I am developing sms based service platform. In India, we have two different types of routes to send sms - promo & trans. Sms sent via promo route has to be checked against nationally maintained ...
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2answers
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Save history editable data RDBMS

I want to make application like testing system. Every question has one or many variant of answers (and one or many can be right). I apologize that tutors and students use my testing system. It means ...
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2answers
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Identity Column in Concurrency, Multithreading, Parallel Processing

Our company would like to understand the effects: If we have single table with Primary Key Identity column, int primary key IDENTITY(1,1), and the Application is conducting multi-threading parallel ...
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2answers
2k views

Is unique index better than unique constraint when an index with an operator class is required

Postgres docs say: The use of indexes to enforce unique constraints could be considered an implementation detail that should not be accessed directly. One should, however, be aware that there's no ...
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2answers
1k views

SQL order by query results in any arbitrary (but reproducible) manner

For testing purposes I need to get some data from a set of database tables in any arbitrary (but reproducible) order. The idea being that I can later compare two runs using a textual diff tool. Is ...
3
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2answers
5k views

Best design for a tree-like structure database

I'm designing a database in MS Access which is used for tracking the locations of a variety of chemical solutions, made in batches. Each batch can be split (aliquoted) practically indefinitely. That ...
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3answers
438 views

Understanding data abstraction levels

The three-level ANSI SPARC Database Architecture suggests three data abstraction levels, namely, external, conceptual, and internal levels. If I understand correctly, the external level represents ...
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0answers
182 views

Aggregation Vs Ternary relationship

I am reading a book about database systems and in the chapter covering database design using ER, the author aims to explain when to use aggregation versus ternary relationship. In short, each Project ...
2
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1answer
248 views

MS Access + SQL Server for 1160 users - Is it worth it? (Please Help!) [closed]

Our school in Delhi (India) wants to develop a professional and robust in-house database (SIS) that should handle vast amount of student information, including admissions, registration, re-enrollment, ...
2
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1answer
3k views

Bicycle Sharing Scheme - ER Diagram [closed]

Please compare the directions below to my ER Diagram and tell me if anything is wrong with my ER Diagram Please I think its accurate enough. Oxford City Council is preparing to launch an innovative ...
2
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1answer
653 views

Multiple values in lookup fields

I know newer versions of MS Access allow multiple selections in lookup fields. For example, if I'm collecting information on my students, I can have a field called Race with lookup values that ...
2
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1answer
2k views

Restrict two specific column values from existing at the same time

I have a PostgreSQL example table where at most one row that is not of type 'c' should be allowed. I would appreciate any help creating a constraint that will enforce this. CREATE TABLE example ( ...
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2answers
194 views

Is this db/table structure sensible?

I'm not very experienced in database design so bear with me. I've taken over a ruby/rails app. with a connected MySQL/innodb database. As I'm updating the server to the latest ruby/rails version I ...
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3answers
409 views

designing a database with type and sub type

I am trying to build a publications database, and i want to develop a genre relation that has various (maybe look up tables) sub-genres attached. as an example, in the genre relation there would be a ...
1
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3answers
179 views

Relational tables with same content, custom solution

So let`s say that I am building an app where I can add comments for FOO. Normally I would have something like this: Table foo and table foo_comments, where foo_comments contains id, foo_id and other ...
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3answers
3k views

Remove duplicate values from query result

I am using Postgres 9.3.9. I have 2 tables : f_agent : CREATE TABLE f_agent ( f_agent__id bigserial NOT NULL, f_agent__total_users integer NOT NULL, f_agent__dim_time_id integer NOT NULL, ......
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1answer
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Database design for dentists

I have a homework, where I should create a database for a dental clinic using MySQL Workbench. This database will be used later for a web app for dentists. Here is a picture of the database design: ...

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