Add to Favorites    Make Home Page 2269 Online  
 Language Categories  
 Our Services  

Home » ASP Home » Database Home » Why should I avoid NULLs in my database?


Search Projects & Source Codes:

Title Why should I avoid NULLs in my database?
Category ASP » Database
Hits 370244
Code Select and Copy the Code
Joe Celko said it best: "NULLs confuse people..." (SQL For Smarties, ISBN 1558605762). McGoveran and Date add: "NULLs...are far more trouble than they are worth and should be avoided; they display very strange and inconsistent behavior and can be a rich source of error and confusion." (Guide to Sybase and SQL Server, ISBN 020155710X). My sentiments exactly. Of course, I don't expect to convince you by flashing a few quotes from very reputable authors in front of you. Let's talk for a minute about what exactly NULLs do that cause this type of reaction. The first problem is that the definition of NULL is "unknown." So, one problem is determining whether one value is (not) equal to another value, when one or both values are NULL. This trickles down to many problems for a database engine and any associated applications. The following list details some of those problems: @li they are interpreted differently depending on compatibility level and ANSI settings; For example, let's consider two values, x and y, that are both NULL. Since the definition of NULL is unknown, then you can't say x = y. However, with the ANSI setting ANSI_NULLs, this can be different. When this setting is FALSE, x = y ... however, when TRUE, x <> y. Confusing, no? @li the storage engine has to do extra processing for each row to determine if the NULLable column is in fact NULL -- this extra bit field affects storage and indexing, and obviously has performance implications for general queries; @li they produce weird results when using calculations, comparisons, sorting and grouping; @li they create problems with aggregates and joins, such as different answers for COUNT(*) vs. COUNT(fieldname); @li they produce unpredictable results in statistics computations, particularly WITH ROLLUP and WITH CUBE; @li applications must add extra logic to handle inserting and retrieving results, which may or may not include NULL values; @li they cause unpredictable results with NOT EXISTS and NOT IN subqueries (working backwards, SQL determines that NULL columns belong or do not belong to the result set, usually for the wrong reasons); @li no language that supports embedded SQL has native support for NULL SQL values.

Related Source Codes

Script Name Author
ııııııııııııııııııııı VyomWorld
Resistor color code reader A.Chermarajan.
Telephone Directory dhivya
card swapping game (Mini Project) nityanand
simple hangman-pascalsource Seabert
college dirtectory (Mini Project) msridhar
Poll Application John van Meter
ASP Daily Hit Counter. Tejaskumar Gandhi
To avoid null in asp environment using sql Sami
Maklumbalas webmaster
poll John van Meter
EasyASP Template Engine. TjoekBezoer
Basic Calculator using HTML & Javascript. Patrick M. D Souza
What servers support ASP ? VyomWorld
What is ASP? VyomWorld


Google Groups Subscribe to SourceCodesWorld - Techies Talk

Free eBook - Interview Questions: Get over 1,000 Interview Questions in an eBook for free when you join JobsAssist. Just click on the button below to join JobsAssist and you will immediately receive the Free eBook with thousands of Interview Questions in an ebook when you join.

New! Click here to Add your Code!

ASP Home | C Home | C++ Home | COBOL Home | Java Home | Pascal Home
Source Codes Home Page


Google Search


Source Codes is a part of Vyom Network.

Vyom Network : Web Hosting | Dedicated Server | Free SMS, GRE, GMAT, MBA | Online Exams | Freshers Jobs | Software Downloads | Interview Questions | Jobs, Discussions | Placement Papers | Free eBooks | Free eBooks | Free Business Info | Interview Questions | Free Tutorials | Arabic, French, German | IAS Preparation | Jokes, Songs, Fun | Free Classifieds | Free Recipes | Free Downloads | Bangalore Info | Tech Solutions | Project Outsourcing, Web Hosting | GATE Preparation | MBA Preparation | SAP Info | Software Testing | Google Logo Maker | Freshers Jobs

Sitemap | Privacy Policy | Terms and Conditions | Important Websites
Copyright ©2003-2024, All Rights Reserved.
Page URL:

Download Yahoo Messenger | Placement Papers | Free SMS | C Interview Questions | C++ Interview Questions | Quick2Host Review