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Database Ex.1 - ANSWER
Name: ____________
Class: __________(
)
Grade: ___________
1.
Fill in the blanks:
(a) A ___field_____ is the lowest level logical unit.
(b) A ___record______ is a logical group of related fields.
(c) A ___file / table_____ is a logical group of related records.
(d) A ____database__ is a logical group of related files.
2.
Data redundancy can be found in some poorly designed databases. This may affect the data
integrity of a database.
(a) What is the meaning of data redundancy?
Data redundancy means storing the same data in multiple locations.
(b) What is the meaning of data integrity?
Data integrity means that data are logically consistent. It refers to the quality of data.
OR
Data integrity refers to the validity, accuracy and correctness of data.
(c)
Explain how data redundancy can affect data integrity.
If data updating in the database is not thorough, the same data may have different values
in different locations. This may cause a loss in data integrity.
(d)
What is the consequence of a system of which the data integrity is affected by data
redundancy?
The consequence of losing data integrity is that the system becomes unreliable.
Information stored becomes useless.
3.
Explain the term "structural independence" in database.
It means program-data independence. The change of structure of a file does not require the
computer programs that access the file be modified.
4.
DBMS system has to tackle "atomicity problem". Explain the term with an example briefly.
It means that all activities in a transaction is either completely performed or undone.
For example, if money is transferred from a saving account to a stock account, the saving
account will be debited whereas the stock account will be credited with the same amount. The
corresponding transaction has to ensure that both data changes are done as one single unit.
5.
Explain the term "data mining" briefly.
It refers to the analysis of data in databases to look for data trends or anomalies.