4.10 Fundamentals of databases

Question 1

`What are the characteristics of serial files? (3)

Answer 1

1. data is stored in the order in which it is entered
2. No order to the data is maintained
3. useful for storing transactional and initialisation files

Question 2

What are characteristics of a sequential file (3)

Answer 2

1. stores data in the order of a key field
2. order is maintained when new records are added.
3. useful for storing master files

Question 3

What is a database? (1-2)

Answer 3

A structured persistent collection of data.

Question 4

What components must a database have (2)

Answer 4

1. tables that store data in rows and columns
2. queries with which to manipulate data

Question 5

Advantages of using a database when handling large datasets ( 4)

Answer 5

1. Makes processing more efficient
2. Reduces storage requirements
3. Avoids redundancy
4. Allows different users to only see relevant data.

Question 6

Which additional layer of software manages the database (1)

Answer 6

The DBMS - database management system

Question 7

What services does the DBMS provide
(5)

Answer 7

1. A language with which to manipulate data.
2. Additional security
3. Structural integrity
4. Program/data independence.
5. An interface for other programs to use data.

Question 8

What is a flat file database? (3)

Answer 8

Allows the user to specify data attributes for only one table at a time

storing those attributes independently.

There is no link between the different tables.

Question 9

What is a relational database(2)

Answer 9

Similar to flatfile, but allows user to specify information about the tables and the relationships between them.

Question 10

What is normalisation (1)

Answer 10

concept of splitting up tables in a database and arranging the data to move it from 1NF, 2NF and 3NF

Question 11

When is table in 1st normal form (2)

Answer 11

1. if it contains no repeating attributes or groups of attributes
2. All attributes must be atomic

Question 12

what does atomic mean in the concept of normalisation (1)

Answer 12

A single attribute cannot consist of two data items such as first-name and surname.

Question 13

What is a composite key (1)

Answer 13

A combination of two or more columns in a table that can be used to uniquely identify each row in the table.

Question 14

When is 2NF achieved (2)

Answer 14

1. Must be in 1NF
2. No partial dependencies

Question 15

In the context of normalisation what are partial dependencies ? (1)

Answer 15

One or more attributes depends on one part of the primary key ( only in cases of composite keys0

Question 16

What are the three keywords used in deleting from a data table using SQL

Answer 16

DELETE FROM(table) WHERE(condition)

Question 17

Keywords used when inserting a new row into a table

Answer 17

INSERT INTO(table) VALUES(values)

Question 18

Selecting data from a table using SQL

Answer 18

SELECT (fields) FROM (table) WHERE condition

Question 19

Inserting specific data into a table

Answer 19

INSERT INTO (table) ((fields)) VALUES(values)

Question 20

Keywords for updating values in a datatable

Answer 20

UPDATE
SET
WHERE

Question 21

What is transaction processing

Answer 21

Any information processing which is divided into individual, invisible operations

Question 22

What base functionalities do all relational database systems (4)

Answer 22

CREATE
READ
UPDATE
DELETE

Question 23

What does a client - server database provide

Answer 23

Provides simultaneous access to the database for multiple clients, known as concurrent access

Question 24

How can the problem of updates be lost if two clients edit a record at the same time fixed

Answer 24

Record locks, a record is locked when a user retrieves it for editing or updating

Question 25

What is serialisation / timestamp ordering

Answer 25

every record has a read and a write timestamp. When trying to write to a record, if the read timestamp is not the same as when it was originally accessed the Database Management System knows that another user has accessed the record.

Question 26

What is commitment ordering

Answer 26

In commitment ordering, no transactions are lost if two users try to access the same record at the same time. Transactions are ordered by their dependencies.