Data Terminology

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Data

Terminology

Database

A series of tables used to store

data

Database software is called a Database

Management System (DBMS)

Tables are

sometimes referred to as files

Fields and records

Within each table, there are columns of

data holding different data items. These columns are called fields

The rows in the table contain all the

information about one entity in the database, such as a person, or an

order, or a car (depending on what the database is storing details of).

This is called a new record

Within each table, there should be one

field that is unique for each record. This is called the key field

To ensure the key

field is always unique, it is often set to be automatically generated by

the DBMS

Each field needs to

have a set data type such as Text

(SQL uses VARCHAR instead of text), Integer, Boolean, Date

Relational databases

Databases containing only one file are

called Flat File Databases

Most databases use tables that are

linked together. This is called a Relational Database

In a relational

database, the tables are linked by a common field. This is usually a key

field of one of the tables. A field that is linked to a key field of

another table is called a Foreign Key

Consequences of

relating tables

When a relationship is set up between

tables, the link will ensure that data integrity is maintained

This means that changes will not be

allowed to data in one table if it will undermine the link to the data in

the other table E.g. if we were to delete doctor 133

from our table, there would be 2 patients with a link to a non-existent

data

To delete doctor

133, we would first have to assign a different doctor to her patient in

the patient table, thus freeing up the link

Spreadsheet or database

Spreadsheets and

databases look similar. It’s important to know the difference. The main

issues are that spreadsheet cell values can change as they can contain a

formula

Spreadsheet column

can all contain a mixture of data types. All data in a column of a

database must be the same data type

Spreadsheets

can only be used by one person at a time, whereas databases ca be set to

allow by lots of users at once

Indexes

Databases indexes help the DBMS sort and find records more

quickly they work like an index in a book using the index of a book helps you

to find a piece of information without having to read the whole book a database

index means the DBSM will be able to find data without having to scan the whole

document. Indexes can be set up on any of the fields in a table but too many

indexes can take up more storage space and increase the time taken to add

delete and update data. Fields that are more likely to be searched for

frequently should be indexed as this will make the searches faster.

SQL- Structures Query Language

Databases can also be created using programming technique

the language used to create and manipulate databases is called SQL or

structured query language

Create Table MyTable(

Field1 database,

Field2 database,

Field3 database,

Field4 database);

Insert into the table:

INSERT INTO MyTable(ID,Fname, Sname, Age)

VALUES (

1,

‘Caitlin’

‘BG’

15);