EAV (“Entity-Attribute-Value”) tables result from a very common schema design error for programmers who started with an OO language, and now work with NoSQL (attribute, value) pairs or a loosely typed programming language. This one schema is supposed to model every possible entity in the universe, but comes with multiple challenges. The most common reasons for using EAV are: You do not have a NoSQL or XML tool in the shop, you have no idea what the data is going to be like, the data is a fruit salad of things.
Read the 9-page whitepaper “The EAV of Destruction” by Joe Celko to learn about EAV tables and how to work with them using SQL queries. The whitepaper describes the key-value format, how EAV works, why use EAV, and where to go next.
Click here to download the whitepaper.
The author, Joe Celko, is the author of a series of ten books on SQL and RDBMS (MKP/Elsevier) that have been in print for over 20 years. He served for 10 years on the ANSI/ISO database standards committee. He has written columns and articles for the IT trade press for over 30 years. He currently enjoys being a TEALS volunteer and judging the local High School Science Fest once a year.
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