1.3.2 Databases

Question 1

Relational Database

Answer 1

“Allows the user to specify information about multiple tables and the relationship between those tables”

Question 2

Flat File

Answer 2

“A database that allows the user to specify data attributes (columns, databases etc.) for only one table at a time, storing those attributes independently”

Question 3

Primary Key

Answer 3

“A field that uniquely identifies a record in a table”

Question 4

Foreign Key

Answer 4

“The linking field in the foreign table formed when a relationship is made. The FK becomes by default the PK of the new table.”

Question 5

Concatenated Primary Key

Answer 5

“When more than one field is added together to form a unique primary key for a table.”

Question 6

Secondary Key

Answer 6

“A key field which can be used to access a table in a different way”

Question 7

ERM

Answer 7

Entity Relationship Modelling: “The process of producing a data model for describing the data or information aspects of a business domain or its process requirements, in an abstract way that lends itself to ultimately being implemented in a data such as a relation database.”

Question 8

Normalisation

Answer 8

“The process of arranging data in tables and setting their relationships to move them through normal forms”

Question 9

Indexing

Answer 9

“The process of creating a database index, which is a data structure that improves the speed of data retrieval operations on a dataset table at the cost of additional writes and storage space to maintain the index data structure.”

Question 10

0NF

Answer 10

“A table with no normalisation. All data and all fields in one table”

Question 11

1NF

Answer 11

First Normal Form: “A relationship with repeating groups removed. That is a relation in which the intersection of each tuple and attribute contains one and only one value.”

Question 12

2NF

Answer 12

Second Normal Form: “A relation that is in 1NF and every non-primary key attribute is fully dependant on the primary key. That is, all the incomplete dependencies have been removed”

Question 13

3NF

Answer 13

Third Normal Form: “A relation that is in 1NF and 2NF, and in which no non-primary key attribute is transitively dependent on the primary key. That is, all non-key elements are fully dependent on the primary key”

Question 14

Normal Forms

Answer 14

“A way of structuring the data in a relational database according to formal rules, in order to avoid problems of efficiency and security in accessing and maintain the data.”

Question 15

SQL

Answer 15

Structured Query Language: “The language and syntax used to write and run database queries”

Question 16

Referential Integrity

Answer 16

“A measure of the consistency of the data in a database. It is violated when the relation to which a foreign key refers to no longer exists.”

Question 17

Transaction Processing

Answer 17

“Information processing that is divided into individual, indivisible operations, called transactions. Each transaction must succeed or fail as a complete unit, it can never be only partially complete.”

Question 18

ACID

Answer 18

Atomicity, Consistency, Isolation, Durability: “A set of properties that guarantee that database transactions are processed reliably. In the context of databases, a single logical operation on the data is called a transaction.”

Question 19

Record Locking

Answer 19

“A technique of preventing simultaneous access to data in a database, to prevent inconsistent results. The classic example is demonstrated by two bank clerks attempting to update the same bank account for two different transactions.”

Question 20

Redundancy

Answer 20

“Redundancy occurs in database systems which have a field that is repeated in two or more tables For instance, when customer data is duplicated and attached with each product bought, then redundancy of data is a known source of inconsistency since customer might appear with different values for given attributes.”