Databases

Question 1

atomicity definition

Answer 1

all transactions should either succeed or fail, and never only partially processed

Question 2

consistency definition

Answer 2

each transaction must obey the defined validation rules of the database to maintain referential integrity

Question 3

durability definition

Answer 3

once a transaction has begun, it must be completed under all circumstances

Question 4

entity-relationship modelling definition

Answer 4

a method of abstractly describing the data tables and the relationship between them visually

they can be used to reduce redundancy and construct a relational database

Question 5

1NF definition

Answer 5

first normal form

a table with no repeating attributes

the intersection of each record and attribute produces exactly one value

Question 6

flat file database definition

Answer 6

a database where a single table structure is used to store all the data

Question 7

foreign key definition

Answer 7

a linking attribute that joins two tables in a relational database by being a primary key in one and a foreign key in the other

Question 8

indexing definition

Answer 8

the process of creating an index of primary keys such that the location of any record can be retrieved given its primary key

Question 9

isolation definition

Answer 9

no transaction should overwrite other transactions that are simultaneously occurring

the same results must be obtained if transaction that are concurrently or sequentially processed

Question 10

normalisation definition

Answer 10

the formal process of optimally designing data tables by reducing data redundancy and repetition by converting them into normal forms

Question 11

primary key definition

Answer 11

a unique identifier that identifies each record in a table

Question 12

record locking definition

Answer 12

a technique used to prevent simultaneous access to data in a database by locking a record when it is being edited or updated

otherwise, inconsistencies may arise in the database

Question 13

redundancy definition

Answer 13

the unnecessary repetition of a field in multiple tables

databases should have redundancy in the form of identical copies if part of the database gets lost and needs to be recovered

Question 14

referential integrity definition

Answer 14

the idea of keeping a database consistent by ensuring that any changes made to data or relationships associated with a table are accounted for in all the linked tables

Question 15

relational databases definition

Answer 15

a database where separate tables are made for each entity, and relationships between entities are represented by foreign keys

Question 16

secondary key definition

Answer 16

a key that can be used as an alternative index to access or sort records in the table in a quicker, but less accurate way than the primary key

Question 17

2NF definition

Answer 17

second normal form

a table in 1NF that has data that repeats across multiple records removed and put into a new table with appropriate relationships (no partial dependencies)

Question 18

3NF definition

Answer 18

third normal form

a table in 2NF where all attributes that are not the primary key are fully dependent on the primary key (no non-key dependencies)

Question 19

transaction processing

Answer 19

the idea of making sure that any logical operation or change in state of a database (transaction) conforms to ACID (atomicity, consistency, isolation, durability) rules for reliable processing

Question 20

what is a relational database

Answer 20

a database which recognises the difference between entities and uses different tables for each entity

Question 21

what is an entity

Answer 21

an item of interest about which information is stored

Question 22

what is a flat file

Answer 22

a database that consists of a single file usually about one entity

Question 23

what is a primary key

Answer 23

a unique identifier for each record in a table

Question 24

what is a foreign key

Answer 24

the attribute which links two tables together

Question 25

what is a secondary key

Answer 25

an index other than the primary key used to search and sort through the database with more convenience and speed

Question 26

what is normalisation

Answer 26

this is the process of coming up with the best layout for a relational database

Question 27

what does normalisation try to accomplish

Answer 27

- no redundancy (unnecessary duplicates) - consistent data throughout linked tables - records can be added and removed without issues - complex queries can be carried out

Question 28

what is an index

Answer 28

an index is a data structure used to look up and access data in database quickly

Question 29

is the primary key automatically indexed

Answer 29

yes

Question 30

what does capturing data mean

Answer 30

capturing data is the process of getting the information you wish to see

Question 31

what method do banks use to capture data from cheques

Answer 31

they use Magnetic Ink Character Recognition (MICR) to get all the details apart from the amount which must be entered manually

Question 32

what does selecting data mean

Answer 32

selecting data is the process of reducing excess information to obtain only the data you require

Question 33

what does managing the data mean

Answer 33

managing the data means to manipulate the information in any type of way as though sorting through it or selecting certain parts using SQL

Question 34

what is the most common language used to manipulate data in databases

Answer 34

SQL

Question 35

what are requirements to be in the first normal form

Answer 35

to be in first normal form there must be no attribute that contains more than a single value in a cell

Question 36

what are requirements to be in the second normal form

Answer 36

- the database is in the first normal form - there are no partial dependencies (no composite keys)

Question 37

what are the requirements to be in the third normal form

Answer 37

- the database is in the second normal form - there are no non-key dependencies

Question 38

what does SQL stand for

Answer 38

Structured Query Language

Question 39

what is SQL

Answer 39

a declarative language used to manipulate databases

Question 40

what is referential integrity

Answer 40

referential integrity is the process of ensuring consistency as it makes sure that information is non removed if it is required elsewhere in a linked database

Question 41

what is a transaction defined as

Answer 41

a transaction is a single operation executed on data

Question 42

what does ACID stand for

Answer 42

atomicity, consistency, isolation, durability

Question 43

what does Atomicity (in ACID) stand for

Answer 43

a transaction must be processed in its entirety or not at all

Question 44

what does consistency (in ACID) stand for

Answer 44

a transaction must maintain referential integrity rules between linked tables

Question 45

what does isolation (in ACID) stand for

Answer 45

simultaneous execution of transactions should lead to the same result as if they were executed one after the other

Question 46

what does durability (in ACID) stand for

Answer 46

once a transaction has been executed it will remain so regardless of the circumstances

Question 47

what is record locking

Answer 47

record locking is the process of preventing simultaneous access to a record

Question 48

what is the name of an issue that can arise as a result of record locking

Answer 48

deadlock

Question 49

what is redundancy

Answer 49

the process of creating more than one copy of data in a physically different location