AICE Computer Science Unit 7

Databases & Flowcharts/Pseudocode

Database

An organized collection of data that is electronically stored and accessible through a database management system (DBMS)

Issues with File Based Approach

• Data integrity Issues - incorrect or incomplete data​

• Data privacy issues​ - All departments must access whole files or folders ​

• Redundancy - Same data stored more than once​

• Data dependency​ - Location of files. File systems can be difficult to navigate if your do not know the storage structure​

Relational Database

Data is stored in a relation, or a special type of table. Each column has a label and contains attributes​. Each Row (tuple) contains information pertaining to one instance of the table​

Referential Integrity

• Prevents data from being entered when no reference is found in other tables​

• Catches errors for data that does not match referencing values​

• Ensures data integrity in DBMS

DBA

• Database Admin uses the DBMS developer interface to create tables, define keys and attributes and search and collect data points for use by the company.

• The DBA has access to the query processor, which uses a Structured Query Language (SQL) to create a Query

Query

A selection of data that has defined conditions.​

SQL DDL (Data Definition Language)

SQL DML (Data Manipulation Language) 1

SQL DML (Data Manipulation Language) 2

SQL DML (Data Manipulation Language) 3

1nf

• Must have a primary key​

• every value for an attribute must have atomicity (one value only)​

2nf

• Fulfil the requirements of first normal form​

• Each non-key attribute must be functionally dependent on the primary key

3nf

• Every attribute that is not the primary key must depend on the primary key and the primary key only.​

• Involves further breakdown of attributes into their own table. No repeating attributes besides PK.​