Week 4: Reading Notes

1) Database: http://en.wikipedia.org/wiki/Database

Databases - organized collections of data, referring to the data itself, not a database management system (DBMS)

Popular DBMSs: Oracle, Microsoft SQL Server, My SQL, and SQLite

Database languages: data definition languages (DDL), data manipulation languages (DML), query languages

Popular database language: SQL - which combines functions of DDL, DML, and query languages

Relational Model
-applications should search for data by content, not by following links
-somewhat limited depending on data type, relational model venders extended their services to support a larger variety of data types

General-Purpose DBMSs
-not always optimal, when considering certain specialized jobs
-DBMS developers, application developers, database administrators, and application end-users are those involved with a general-purpose DMBS

Examples of Database Types:
-Active database
-Cloud database
-Data warehouse
-Distributed database
-Document-oriented database
-Embedded database

Data Models: provides a way to use data structures needed to model an application
-Hierarchical
-Network
-Relational
-Entity-relationship

Database Architecture: may be considered an extension of data modeling.
-External level - how each end-user understands data organization
-Conceptual level - takes all external views and organizes into one coherent view
-Internal level - concerned with database implementation

Database Security
-Access control
-Data security
-Database audit

DBMS Architecture: specifies components and their interfaces
-external interfaces
-database language engines
-query optimizer
-database engine
-storage engine
-transaction engine
-DBMS management and operation component

Database Transactions
-All transactions obey the following rules: ACID (Atomicity, Consistency, Isolation, Durability)

2) Entity relationship model in database: http://en.wikipedia.org/wiki/Entity-relationship_model

Entity relationship model (ER) - abstract and conceptual representation of data
-ER diagrams are drawn with “rectangles to represent entities, and diamonds to represent relationships.”

Semantic Model - a model of concepts

Crow’s Foot notation - boxes (instead of rectangles) and lines (instead of diamonds)


3) Database Normalization Process: http://www.phlonx.com/resources/nf3/

Database Normalization Process:

Three forms to memorize:

1. No repeating elements or groups of elements
2. No partial dependencies on a concatenated key
3. No dependencies on non-key attributes