IGCSE ICT Chapter 5

Advantages of flat-file database over relational database

Easier to set up. Easier to understand. Simpler sorting. Simpler filtering.

Data types

1. Numeric Data 2. Alphanumeric/Text Data 3. Boolean/Logic Data 4. Data/Time Data

File

A collection of related records (eg. Table containing all info about all students in one school).

Definition of database

A database is an organized collection of data related to each other.

Relational databases: Foreign keys

A primary key in another table used to create a relationship between two tables.

The data type of telephone numbers

Alphanumeric because it starts with zeroes, contains symbols and spaces and cannot be used in arithmetic operations.

Data validation

Checking that data entered to a computer is sensible.

Field

Column reserved for one particular item of data (eg. Student name column).

Visual check

Comparing entered data with original source

Double data entry

Entering data twice then comparing the two versions.

Database terminologies

Field (Columns) (|||) Field names (titles) Record (Rows) (===) File Primary/Field key

Primary/Field key

Field that uniquely identifies a record (eg. Student ID)

Database types

Flat-file databases (all data held in one single table). Relational databases (two or more linked tables).

Record

Group of related items of data (eg. All info about one student).

Types of numeric data

Integers. Real numbers. Currency. Percentage.

Proofreading

It is reading through the document without referring to the original source. Proof reading is different from double data entry.

Relational databases: Relationships

Link or association between fields.

Advantages of relational database over flat-file database

No duplication of data, less data entry. Less errors. Saves storage space. Easier to add and delete data. Better security.

Relationship types

One-to-one One-to-many Many-to-many

Validation checks

Presence check. (Must fill) Lookup check. (List) Range check. (Within acceptable values) Length check. (Number of characters) Type check. (Correct data type) Format check. (Pattern) Check digit. (Used in barcodes)

Field name

Title given to each field.

Data verification

Visual check. Double data entry.