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Semester 1/DatabaseBackup/Week 1/Week 1 Database Systems.md

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+## Lecture 1 (13:00) Organisation
+
+### 32741 ( Module Code )
+
+### Module Information
+
+- 67 hours of private study across all modules in semester 1
+- Exercise booklet on blackboard
+- Semester 1 Coursework 50%
+- Semester 2 Coursework 50%
+
+### Reading
+
+- Preface, C.1 & C.2 of exercise booklet.
+
+## Lecture 2 (15:00) Introduction
+
+### Applications of Databases
+
+- Supermarket
+	- Barcode DB
+	- Price Retrieval
+	- Stock Control
+- Credit Card
+	- Credit Limit Check
+	- Security Check
+- Other
+	- Library
+	- Websites
+
+### File-Based Systems
+
+- Attempt to digitise information
+- Collection of application programs
+- Each performs a front end interface
+- Each manages and defines its own data
+- Limitations lay the foundations to what we have now
+
+#### Limitations
+
+- **Separation** and **isolation** of data
+- **Incompatible** file formats
+- **Fixed queries** (written by the developer, not the end user) / proliferation of application programs
+- Data **duplication**
+	- Costs money and time to enter data multiple times
+	- **individual**, **independent** instances of data
+	- Additional storage space taken
+	- **Loss of data integrity** and parity (consistency lost), since they are individual sources of data.
+	- Ex. Payroll and Personnel data duplicated across DB
+- Data **dependence**
+	- **Physical structure** / storage of data / records is defined in **application code**
+	- Difficult to change structure
+	- Programs have to be modified if structure needs changing
+
+### Databases
+
+- Shared collection of **logically related** data (+ **description**), designed to fit needs.
+- **Self-describing** collection of integrated records
+
+#### Database System
+
+1. Collection of data stored on files
+2. Database Management System ( Interface )
+3. Variety of users
+
+### Database Management System
+
+- Software that enables the **creation**, **definition**, and **maintenance** of databases. and provides **controlled access**.
+- User Interaction is provided through User Programs (Queries), examples of include:
+	- Add Data
+	- Delete Data
+	- Update Data
+	- Retrieve Data
+
+#### Functions of DBMS
+
+- Data Integration
+	- Stored **efficiently**
+	- Minimises **duplication** and **redundancy**
+- Data Integrity
+	- No **corruption** or **inconsistency**
+- Data Security
+	- Data is not lost or made inconsistent through system failures, or through deliberate corruption.
+- Data Independence
+	- **Isolates users** from physical data
+	- User has logical model interface of database
+
+#### Users of a DB Environment
+
+- Data Admin
+	- Consults and advises senior management
+	- Ensures database serves its purpose
+- Database Admin
+	- Technically oriented
+	- Ultimate control over data structure and access
+- Database Designers
+	- Designs structure of database to cater to needs
+- Application Programmers
+	- Designers of end user applications
+- End Users
+	- Clients who require access to the database
+	- No control over function of the applications
+	- May have little to no knowledge on back-end
+
+#### Advantages over File-Based
+
+- **De-Duplication**
+- Lowers risk of inconsistency
+- More users share more data
+- Improved **Security**
+- Improved **accessibility** and **responsiveness**
+	- Department boundaries crossed, data is **no longer independent**
+	- Provides **query** language
+	- **On-demand** access
+- Improved **productivity**
+	- Provides many standard functions programmers would have to hard code
+- Improved **maintenance**
+	- Separates data descriptions from applications
+- Improved **backup** and **recovery**
+
+#### Disadvantages
+
+- **Complicated**
+- **Large** / Heavy
+- **Expensive** setup
+- May incur **additional storage** space
+- **Cost** of conversion
+- **Performance** may not be as good as file-based
+- Higher **impact of failure**
+
+### Relational DBMS
+
+- Dominant DBMS in use
+- Estimated sales of $15-20m/year
+- Established in 1970
+- Simple logical structure
+
+#### Relational DB
+
+- Stored in files called relations (tables)
+	- Consists of rows and columns
+	- Carries data on one kind of entity ex. Cars
+- Commonly addressed as entity-name(attributes). Ex. Cars(Model, Age, Colour)
+- Primary Key - The identifying attribute of a table. Ex. Registration Plate (Unique)
+- Goal is to remove as much redundant data as possible.
+- Foreign Key - another unique key to provide an index to another table.
+	- Attribute that is linked to the primary key of another table
+
+### Reading
+
+- C.1 Connolly & Begg (2014 & 2004)
+
+## Workshop 1 (9:00)
+
+```
+SELECT *
+FROM [Customers];
+WHERE [Country] = "Germany";
+```
+
+```
+SELECT *
+FROM [Customers];
+WHERE [Country] = "Germany" AND [ContactTitle] = "Sales Representative";
+```