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.