The logical model and/or physical design of a database.

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3answers
365 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
192 views

Data modeling with many attributes where few apply to each record [closed]

I'm pretty new to data modeling, so please excuse me if I've missed something obvious. I'm trying to decide on a schema (or possibly a DBMS) to work with some data where there are quite a few possible ...
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1answer
236 views

What is the advantages of using auto_increment in database as primary key over set of attributes?

I have table as CREATE TABLE circle ( circle_id int(11) auto_increment primary key not null, user_id int (11) not null, title varchar(255) collate utf8_general_ci not null ); CREATE ...
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1answer
1k views

How much the decision to use ternary or binary relationship influences the accuracy of the model with regards to a given business model?

The question title is very long, so here's a little bit of context to (try to) make it clear. I asked a question regarding ternary relationship. The question was Ternary relationship: what's the ...
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1answer
220 views

One to at most one relation or multiple null columns?

I have a table with many attributes that can be grouped in logical groups, and thus the idea of put this attributes in separate tables seems attractive. The logical groups doesn't represent entities ...
0
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3answers
105 views

Which of these database designs is normalized?

I have two possible database designs. A) a many-to-many relationship between Branches and FiscalYears via a dedicated join table FiscalYearsBranches B) two (or more) many-to-many relationships ...
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1answer
1k views

Select rows from table where each row refers to a different schema

I have customer table in public schema. And I have a schema named after each customer. Each customer schema contains different tables like portals, plugin, ... When I want to select portals used by ...
0
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1answer
133 views

When to use a multidimensional relationship in an ERD?

When to use a multidimensional relationship in an ERD? My textbook is in Dutch, and the two paragraphs that explain about multidimensional relationships is too vague and brief. I don't understand when ...
0
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1answer
277 views

Conversion of simple ERD to Table: is the solution below any good?

Consider the following ERD: Suppose that all entities only have two attributes: a PK plus a name/number. I want to convert that ERD to tables. Is it needed 4 tables (1 for each relationship ...
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2answers
2k views

Which schema is better for a shopping project? [closed]

I'm working on a business-to-customer project that has variety of product types. There are a few properties like name, description, brand_id that each product has but there are also many specialized ...
0
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1answer
167 views

What are the first necessary actions needed to help secure a database's schema & data? [closed]

This smells like an open-ended, opinionated, wiki free-for-all, but I'm not trying to make this a battle of opinions. It seems like there should be a good checklist out there for all to agree on ...
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3answers
997 views

What is the optimal data type for an MD5 field?

We are designing a system that is known to be read-heavy (on the order of tens of thousands of reads per minute). There is a table names that serves as a sort of central registry. Each row has a ...
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4answers
2k views

How to store data in a database without tables?

All I learned in school was SQL which saves data to tables. Right now I am working on a project where data is stored in XML-files. Additionally every XML contains a reference to visual files (JPEG). ...
9
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2answers
2k views

How does using separate schemas affect SQL Server 2008 performance?

I want to use separate schemas for objects with different purposes in our SQL Server 2008 database. Right now we use a fairly mind-numbing naming convention to indicate the purpose of a table or ...
9
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4answers
1k views

Where should one put indexes in a time dimension table?

After reading the Questions and Answers from this website about indexes, a question came to my mind. What if, one is using a time dimension table with the lower level of granularity being the day. ...
8
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4answers
576 views

What are the performance considerations between using a broad PK vs a separate synthetic key and UQ?

I have several tables where records can be uniquely identified with several broad business fields. In the past, I've used these fields as a PK, with these benefits in mind: Simplicity; there are no ...
7
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4answers
1k views

How to create a database for unknown kinds of data?

I am in the process of designing a database for a new PHP/MySql-based application. My problem is that I do not and cannot represent what should be saved in the database because it is unlimited and ...
7
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5answers
1k views

Database design: Dividing multiple identical tables, good or bad?

I am very new at SQL and databases in general. I only use them for the occasional homework so I haven't even tried to master them. I have seats at a theater, the seats are divided into 4 main areas ...
6
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2answers
132 views

Creating relationships between tables that where not specified in the given UML diagram

Good evening! I'm working on designing my very first actual database from the following UML class diagram (in French unfortunately): I'm at the point of creating the relational sketch of it which ...
6
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3answers
430 views

Need help on my first ER diagram

I just started my first Database course online, and I have a homework assignment to create an E-R diagram from a list of specifications. The specs are as follows: The company is organized into ...
6
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2answers
15k views

Efficient way of changing VARCHAR to NVARCHAR fields in a large table in SQL Server 2008?

I am aware of when adding new fields to large tables, it is recommended to add them to the end of the fields rather than somewhere in the middle, and wondering if something like this applies when ...
6
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4answers
538 views

Purpose of IDs in a User Table Database

In a table, such as a user table, where there will only be 1 row with a for any particular user, why have an ID field, let alone as the primary key?
5
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3answers
156 views

Tables with FK's of each other

I'm working on a database that stores address information. (Related to this question I posted) I have 2 tables: CREATE TABLE [dbo].[Country] ( [Code] CHAR (2) NOT NULL, [Code3] ...
5
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1answer
881 views

Enforce data integrity with a recursive table

I have an existing oracle 11g database schema that works with a web application. I am planning an expansion to the application so a web service can do data operations on the database. As part of the ...
5
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2answers
33k views

Using Same CASE WHEN Conditions For Multiple Query Columns

Is there a "better" way to rewrite a SELECT clause where multiple columns use the same CASE WHEN conditions so that the conditions are only checked once? See the example below. SELECT CASE ...
5
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2answers
226 views

Is there a name for this “restricted one to many” relationship? Can it be enforced in the DB?

In an application I'm working on, we have a kind of "restricted one-to-many" relationship. I'm wondering if this has a name, and whether it's possible to enforce at the database level. A standard ...
5
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2answers
250 views

Is there a reason/benefit I am not aware of for this kind setup?

I now manage a MySQL database that was designed and created by another. I am confused about a certain setup that the original developer created.. He did not use auto increments for table IDs. ...
5
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3answers
772 views

how do I model this in database?

I am using mysql as my backend database. Here is the use case; A HolidayPackage is configured with some default offerings. These default offerings can be up/downgraded based on the options provided. ...
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2answers
4k views

What Is The Point of a Primary Key?

Why do I need to have a primary key on my database for it to function correctly? In every tutorial I read, you need to make the id key the primary key. What does the primary key do differently than ...
4
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2answers
61 views

Does this simple database design work even if it's cyclic?

I am a graduate student working on breast cancer in a veterinarian facility. I am designing a database to keep track of the health of my mouse colony. Each day, animal care staff verify each cage ...
4
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3answers
169 views

SQL - Many-to-Many relationship with same table and with relationship constraint

I have a SellerProduct table. Each row within the table represents product information as offered by a seller. The SellerProduct table has the following columns: id (serial, pk) productName ...
4
votes
2answers
113 views

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 ...
4
votes
1answer
364 views

Storing phone number in E.164

TLDR; If I store a phone number in MySQL(or any DB with equivalent constraints), would the correct format be E.164 values into a VARCHAR(32) field? Have been reading up on format/storage of ...
4
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1answer
167 views

Non-overlapping rectangles constrained to a boundary

I am trying to model placement of parts on a circuit board. Without any meaningful constraints, my basic schema looks like this: create table part ( part_id bigserial primary key, name text ...
4
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6answers
5k views

using IDENTITY column with increment -1

I need to run a sql server logging db with 2 main tables in 2 seperate datacentres writing to both at the same time. I had the idea of restoring the db to the new datacentre and then reseeding the ...
4
votes
1answer
746 views

SQLite3 simple database design question

I'm an ruby hobbist with no experience at all related to databases. I'm writing an application that is going to gather and backup tweets and blog posts (via rss feed) in an SQLite3 database. The ...
4
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1answer
3k views

Under what conditions are polymorphic associations used? What are the alternatives?

As I understand it, polymorphic relationships among tables in a database allow one table to have one foreign key that references many tables. I have found that tags are a common application of this ...
4
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3answers
4k views

indexes, foreign keys and optimization

Not a DBA so pardon my ignorance... I have a table with 20 fields of which 8 are foreign keys. Mysql has by default added an index for each foreign key. Table has about 100k rows. When retrieving ...
3
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1answer
36 views

Store the content book in database, so that it would be updated afterwards or store them as document?

I have some books in (urdu) made with Urdu Inpage(tool for making pages in urdu) like this: problem that these document files are difficult to read in php because they gives unread-able characters, ...
3
votes
3answers
169 views

Choosing a PK: VARCHAR(2) or SMALLINT(2)?

Today we were discussing the following: Brazil has 27 states and each one has its own abbreviation (just like USA). So we've got RJ for Rio de Janeiro, SP for São Paulo, MG for Minas Gerais and so ...
3
votes
2answers
516 views

PostgreSQL LIKE query on ARRAY field

Is there any way to have a Postgres LIKE query on a ARRAY field? Currently I want something like that: SELECT * FROM list WHERE lower(array_field) LIKE '1234%' Currently lower is not needed that ...
3
votes
2answers
240 views

Use composite type to create new table

In ORDBMS databases I have seen that complex types can be used: create type name as( ...) And I can references those types when creating a new table, like: create table example (row_name ...
3
votes
3answers
111 views

Schema for a lease platform

I have following tables: A room I want to lease (has user.id as ForeignKey) A users table for users who can rent it An availability table for time periods the room is to use with prices for that ...
3
votes
2answers
360 views

Database design for multiple user attributes

I am building an app with Laravel, and I have users which also have a profile. I am unsure about the best way to set up the database for the user attributes. For example: user_ud | name | ...
3
votes
2answers
429 views

Is there a way I can speed up queries against this particular view?

I have three tables in a PostgreSQL database that I'm querying via a view and some joins. CREATE TABLE network_info ( network CIDR NOT NULL, some_info TEXT NULL, ...
3
votes
0answers
48 views

How do I design a database for different sets of measurements on different subjects?

I'm conducting a research project that consists in sampling different physical quantities on about 30 buildings, most of them single-family houses. Some of those physical quantities will be common to ...
3
votes
2answers
259 views

Deciding when to extend to child tables

I have a table of entities. For example purposes, lets call them Vehicles: Car, Boat, Motercycle, etc. I'd ideally like to place all entities in a single Vehicles table because a lot of related ...
3
votes
2answers
189 views

Simple table normalisation

In raw form, I have data with 2 columns: skills in welsh and stats for that skill. For storing these information in a database, would it be best to combine the stats with the categories, or split ...
3
votes
2answers
248 views

Both Primary and Foreign Key Needed on Table?

Someone recently asked this question: There are two tables: Deal and DealCategories. One deal can have many deal categories. So the proper way should be to make a table called ...
3
votes
2answers
336 views

Data Model For Summarizing Student Info

I work for a school district and one of the many things the admin wants to know is how many tardies a student has for a given time frame. I could certainly go retrieve the count from the attendance ...