---
title: "13-databases-1"
aliases: 
tags: 
- cosc203
- lecture
---

# What is a database
- an integrated collection of data
- implicit properties
	- represents some aspect of th real world, called miniworld
	- is a coherent collection of data with inherent meaning
	- is designed built and populated with data for a specific purpose

## DBMS
- a software system designed to store, manage, and facilitate access to the database
- Oracle, SQL erver, MySQL, MonogDB

## Application program
- a program that provides access to the dtabase by sending queries and requests for data to the DBMS

![data base system diagram|400](https://i.imgur.com/3xzWCw6.png)

# This course
- modelling and design of DBs 
- programming  (SQL + appliation development)
- DBMS implementation

specifiically *relational databases*
- ER modelling
- datbase normalisation
- SQL

## relational vs nosql
relation is better for structured data, nosql is better for abstract data, as it is more flexible

# Data modelling
first step in designing database
- create a data model for a specific problem domain

a model is Defn: a collection of concepts that can be used to describe the structure of a database such as data types, relationsips, and contraints that should hold for the data

schema Defn: a collection of metadata that describes the logical view of a database

noSQL databases are either schema-free or have relaxed schemas

![example database schema|400](https://i.imgur.com/09ATkHZ.png)

## conceptual data modelling