In addition to Weibo, there is also WeChat
Please pay attention
WeChat public account
Shulou
2025-03-30 Update From: SLTechnology News&Howtos shulou NAV: SLTechnology News&Howtos > Database >
Share
Shulou(Shulou.com)06/01 Report--
The design of relational database follows six paradigms: the first paradigm (1NF), the second paradigm (2NF), the third paradigm (3NF), the Buss-Cod paradigm (BCNF), the fourth paradigm (4NF) and the fifth paradigm (5NF). First normal form 1NF
1NF, that is, each data column of a database table is an indivisible atomic data item.
Second normal form 2NF
2NF requires that non-code attributes must be completely dependent on candidate codes on the basis of 1NF. That is, there must be a primary key field that uniquely identifies a row of data.
The third normal form 3NF
3NF requires that on the basis of satisfying 2NF, any non-primary attribute does not depend on other non-primary attributes. That is, redundant fields are not allowed. For example, there is a department information table in which each department has a department number (dept_id), department name, department profile, and so on. Then after the department number is listed in the employee information table, the department name, department profile and other department-related information can no longer be added to the employee information table.
Pascod normal form BCNF
BCNF requires that on the basis of satisfying 3NF, any non-primary attribute can not be dependent on the primary key subset.
Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.
Views: 0
*The comments in the above article only represent the author's personal views and do not represent the views and positions of this website. If you have more insights, please feel free to contribute and share.
Continue with the installation of the previous hadoop.First, install zookooper1. Decompress zookoope
"Every 5-10 years, there's a rare product, a really special, very unusual product that's the most un
© 2024 shulou.com SLNews company. All rights reserved.