Please enable JavaScript.
Coggle requires JavaScript to display documents.
Databases (Concept (Flat File Databases (Database consisting of only one…
Databases
Concept
-
A database software has to be able to create, retrieve, update and delete data
-
-
Flat File Databases
-
Fairly small(eg names, addresses and phone numbers)
Made from fields (a characteristic of something stored in a database) and records (all the data about one item in a database)
-
Whenever the nature(column) of it changes, the database has to be completely rewritten
Data Redundancy
-
If it occurs, it can make data very confusing and difficult to edit leading to mistake(eg if someone changes their name, every field has to be changed)
Data Integrity (the state of data being as it should be, reflecting reality)
Validation (the process of checking data as it is input to ensure that it is reasonable, doesn't prevent all errors but detects the breaking of rules)
Verification (the process of checking that data is true or correct, Bar codes/Smart cards/Magnetic strips)
-
Data Models
-
-
Relational Databases
-
Tables: Called a relation, Contain 1 entity(something that we store data about in a database), Has attributes(a characteristic of an entity. It becomes a field in a data table), Linked by primary and foreign keys
Entity Relations
Entity Relation Diagrams (a diagram that shows how different entities used in a database are connected)
To reduce data redundancy, one to many (a relationship where one record in a table may have links to many records in another table) way is used
-
Database Design
Data Type(the software needs to know how to handle the data), Field Size (no point in reserving more bytes for each field than are necessary), Validation (rules set up to filter out some types of mistakes), Key field (choose at least one field for your primary key)
Key Fields
Databases must have a primary key so it has a unique value and can be identifiable with out any mistakes
-
Sharing Data
Large organisations need big databases to store data that is seen and worked on by many different people
These databases need to - Protect data from damage and unintended deletion, Protect data from unauthorised access, Make sure that all who need to gain access can, Supply users with no more than they need to work, Make sure the data is accurate and up to date
-
