What is data redundancy and data integrity?

Data inconsistency exists when different and conflicting versions of the

same data appear in different places. Data inconsistency creates

unreliable information, because it will be difficult to determine which

version of the information is correct. (It's difficult to make correct - and

timely - decisions if those decisions are based on conflicting information.)

Data inconsistency is likely to occur when there is data redundancy. Data

redundancy occurs when the data file/database file contains redundant -

unnecessarily duplicated - data. That's why one major goal of good

database design is to eliminate data redundancy.

In the below link you can find more details.

http://opencourseware.kfupm.edu.sa/colleges/cim/acctmis/mis311/files%5CChapter1-Database_Systems_Topic_2_Introducing_Databases.pdf