background preloader

Ten Common Database Design Mistakes

Ten Common Database Design Mistakes
No list of mistakes is ever going to be exhaustive. People (myself included) do a lot of really stupid things, at times, in the name of “getting it done.” This list simply reflects the database design mistakes that are currently on my mind, or in some cases, constantly on my mind. I have done this topic two times before. Before I start with the list, let me be honest for a minute. So, the list: Poor design/planning Ignoring normalization Poor naming standards Lack of documentation One table to hold all domain values Using identity/guid columns as your only key Not using SQL facilities to protect data integrity Not using stored procedures to access data Trying to build generic objects Lack of testing Poor design/planning “If you don’t know where you are going, any road will take you there” – George Harrison Prophetic words for all parts of life and a description of the type of issues that plague many projects these days. Ignoring Normalization Are there always 12 payments? Maintainability Related:  shiny stufftrier

Five simple database design tips A flawed database can affect all areas of your application, so getting the design right is of paramount importance. Check out Builder's five simple design tips, and share some of your own. If an enterprise’s data is its lifeblood, then the database design can be the most important part of an application. I’ll get the show started by listing my five favorite tips and giving a brief explanation of the rationale behind each one. #1: Use meaningful field namesI once worked on a project I inherited from another programmer who liked to name fields using the name of the onscreen control that displayed the data from that field. Unless you are using a system that restricts you to short field names, make them as descriptive as possible—within reason, of course. #2: Do your homeworkNot only should you research your business needs when designing a new database, you should check out the existing system, as well. Restrict the user from editing the field after the record’s creation.

The one-to-many relationship On the page about linking tables I showed you how data from different tables can be linked by defining a foreign key relationship. You saw how orders are linked to customers by including the customer_id as a foreign key in the orders table. Another example of a one-to-many relationship is the relationship that exists between a mother and her children. (Technically it would be better to speak of a woman and her children instead of a mother and her children, because in a one-to-many relationship a mother can have 0, 1 or many children and a mother with 0 children isn't technically a mother. When one record in table A can be linked to 0, 1 or many records in table B, you are dealing with a one-to-many relationship. A schematic representation of a one-to-manyrelationship. How to identify a one-to-many relationship? When you have two entities ask yourself these questions. How many entities of B can belong to entity A? Examples Some examples of one-to-many relationships are listed below.

Study: China’s ‘Great Firewall’ may not actually isolate Internet users The researchers' visualization of "culturally defined markets" -- the interconnected, language- and geography-based groups into which Internet users naturally separate. The clearest markets in this diagram are English (white), Chinese (red), Japanese (green) and Russian (fuscia). (Northwestern University) Everyone from Hillary Clinton to Amnesty International has bashed China’s “Great Firewall” as an impediment to free speech and democracy. That’s what makes a new study out of Northwestern University both odd and intriguing: According to its authors, media researchers Harsh Taneja and Angela Xiao Wu, Chinese censorship actually has little impact on what people there read online, and Chinese Internet users aren’t particularly isolated, even vis-a-vis users in countries with unrestricted access. What’s more, they essentially argue, the Internet isn’t that grand, global community that connects and equalizes everyone.

database design - Best practices on common person fields (Name, email, address, gender etc...) - Database Administrators My bum is getting sore from sitting on the fence, so I am going to just throw out some answers and hope to not get down-voted into oblivion. Please offer constructive criticism. E-mail Address: min: 6 (a@g.cn) . Or 3 if you want to track local domain email addresses max: 320 254 (RFC) The amount of code to validate an email is actually insane, so let's just assume it's valid if it has a "@" You may want to abstract an email address as a "communication method", so that you can easily list all methods with which to communicate with a user. Gender Gender can change over time, so you could track that if it's important to you. Addresses: NORAM I am gonna take the cheap way out and stick to North American addresses. It is convenient to abstract countries, divisions, cities, and counties mostly due to taxation. GeographicArea: id: int type: {country, division, county, city, indian reservation} name: varchar(45) [1] abbreviation: nullable varchar(4) parent_id: nullable int Address: PartyAddress Names

Unity 3 – April 2013 patterns & practices Developer Center April 2013 Unity is a lightweight, extensible dependency injection container with support for instance and type interception. Overview Unity is a lightweight, extensible dependency injection container with support for constructor, property, and method call injection. Simplified object creation, especially for hierarchical object structures and dependencies. Unity is a general-purpose container for use in any type of Microsoft.NET Framework-based application. In addition, Unity is extensible. This release adds support for Windows Store apps as well as the registration by convention feature to ease the task of configuring Unity. Audience Requirements These reusable components and guidance are intended primarily for software developers and software architects. Contents of This Release Microsoft Unity 3 contains the following: Binaries. System Requirements Supported architectures: x86 and x64. For a rich development environment, the following are recommended:

The many-to-many relationship The many-to-many relationship is a relationship where multiple rows from table A can correspond to multiple rows in table B. An example of such a relationship is a school where teachers teach students. In most schools each teacher teaches multiple students and each student can be taught by multiple teachers. The relationship between beer distributors and the beers they distribute is a many-to-many relationship too. A distributor will in most cases distribute more than one type of beer and each type of beer can be distributed by multiple distributors. Note that in database design the question you should ask yourself is not whether a certain relationship exists at the moment, but if a certain relationship is likely to exist in the future. Modelling a many-to-many relationship A many-to-many relationship is modelled with tree tables. All primary keys must be unique. Beer tables Note that in the tables above the primary keys fields are colored blue and underlined.

The Workshops Of Everything sql - Is there a standard implementation of a Users Database? - Database Administrators Going to have to go for a big old fashion "it depends". Of course you are going to need some sort of key on this table. You could start off with a UserID. This could just be a incrementing INT (or bigint if you are going to have over 2.1 million users). I've seen lots of databases also use GUIDs as the main UserID. You then need to decide how normalized you want your database. I'd keep the main user table to: some sort of ID or PK you can useFirst Name/Last Name or just a usernamesome sort of status of the user (active, disabled, etc) - (tinyint linking to a status table)created date That should be your starting point. From there you could add other columns based on what you want to store. I HIGHLY recommend you read this article though -

Related: