Introduc.on to Databases

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1 Introduc.on to Databases G6921 and G6931 Web Technologies Dr. Séamus Lawless Housekeeping Course Structure 1) Intro to the Web 2) HTML 3) HTML and CSS Essay Informa.on Session 4) Intro to Databases 5) Intro to Databases 6) PHP and MySQL 7) Reading Week 8) PHP and MySQL 9) PHP and XML 10) CMS 11) Analy.cs 12) Visualisa.on 1

2 Housekeeping You all have a Laptop? Can you all get connected to the Internet? Can you all get connected to your webspace through SHH? Can you use a URL to view your files? Assessment Con.nuous Assessment Upload the files you create! Retrieving Web Pages Every page has a unique uniform resource locator (URL) Web pages are stored on web servers that use HTTP to exchange informa.on with client soaware e.g., 2

3 Retrieving Web Pages Client program (browser) uses the local machine to connect to a domain name system (DNS) server DNS server translates the hostname into an internet protocol (IP) address Browser then aeempts to connect to server host using specific port Aaer connec.on, browser sends a HTTP request to the web server to request a page usually a GET request Exercise 1 Use the HTML file from last week s Exercise 4 Add a Background Colour to the whole page Using an inline style to do this 3

4 Exercise 2 Take the HTML file from the previous exercise Change the background colour of each sec.on of the page Using an internal style sheet to do this Exercise 3 Take the HTML file from the previous exercise Change the font, font colour and font size in each sec.on of the page Use an external style sheet to do this 4

5 What is Data? Data is any informa.on that you want to store and refer to again. Data can be: Text Numbers Dates Images Videos Files Any other types of informa.on. For example, if you sell cakes, you can store the names, pictures, and recipes of your cakes, the prices and quan..es of boxes and the dates of sales.. What is a Database? An organised collec.on of Informa.on, or Data Organised to: model aspects of reality in a way that supports processes that require this informa.on A collec.on of Manuscripts in an archive Finding manuscripts by a specific author and where those manuscripts are located mostly, to make the data more useful! 5

6 Advantages Search and Retrieval Filtered according to specific needs Reduced Data Redundancy Ease of Update Greater Data Integrity Independence from Applica.ons, Concurrent Access Improved Data Security Reduced Costs for Data Entry, Storage and Retrieval Databases There are many Database Models Oaen referred to as Data Models The four most common are: Hierarchical Network Rela.onal Object Rela.onal Graph ST3001 MySQL Tutorial 1 - University of Dublin, Trinity College 6

ng Organised hierarchically with parent and child nodes (like a family tree!

7 Hierarchical Database One of the oldest database models Commonly used in Mainframe compu.ng Organised hierarchically with parent and child nodes (like a family tree!) Network Database Also have a hierarchical structure Uses members and owners rather than parents and children. Each member can have more than one owner 7

8 Rela.onal Database Differs from previous models as it is not Hierarchical, but Rela.onal More flexible than either the hierarchical or network database models. Uses no.ons of: Rela.ons (Tables) Tuples (Rows) Aeributes (Columns) Rela.onal Databases A table is the basic storage structure of a Rela.onal Database. A table holds all the data necessary about something in the real world Name, Age, Address, PPS etc. Tables are Two- Dimensional Each Rela.onal Database can contain one or many Tables 8

EMPNO NAME JOB DEPTNO 7856 MCNULTY OFFICER 30 7710 DANIELS LIEUTENANT 40 7992 GREGGS DETECTIVE 10 7428 MORELAND DETECTIVE 20 DEPTNO NAME LOCATION 10 NARCOTICS TOWER 221 20

DEPTNO 7839 KING PRESIDENT 17- NOV- 81 5000 10 7698 BLAKE MANAGER 7839 01- MAY- 81 2850 30 7782 CLARK MANAGER 7839 09- JUN- 81 2450 10 7566 JONES MANAGER 7839 02- APR- 81

CLERK 7698 03- DEC- 81 950 30 7521 WARD SALESMAN 7698 22- FEB- 81 1250 500 30 7902 FORD ANALYST 7566 03- DEC- 81 3000 20 7369 SMITH CLERK 7902 17- DEC- 80 800 20 7788 SCOTT

9 EMPNO NAME JOB DEPTNO 7856 MCNULTY OFFICER DANIELS LIEUTENANT GREGGS DETECTIVE MORELAND DETECTIVE 20 DEPTNO NAME LOCATION 10 NARCOTICS TOWER HOMICIDE CITY CENTRE 30 MARINE DOCKS 40 EVIDENCE DOWNTOWN ST3001 MySQL Tutorial 1 - University of Dublin, Trinity College EMPNO NAME JOB MGR HIREDATE SALARY COMM DEPTNO 7839 KING PRESIDENT 17- NOV BLAKE MANAGER MAY CLARK MANAGER JUN JONES MANAGER APR MARTIN SALESMAN SEP ALLEN SALESMAN FEB TURNER SALESMAN SEP JAMES CLERK DEC WARD SALESMAN FEB FORD ANALYST DEC SMITH CLERK DEC SCOTT ANALYST DEC ADAMS CLERK JAN MILLER CLERK JAN ST3001 MySQL Tutorial 1 - University of Dublin, Trinity College 4 9

10 Table Rela.onships EMPNO NAME JOB DEPTNO 7856 MCNULTY OFFICER DANIELS LIEUTENANT GREGGS DETECTIVE MORELAND DETECTIVE 20 Primary Key Foreign Key DEPTNO NAME LOCATION 10 NARCOTICS TOWER HOMICIDE CITY CENTER 30 MARINE DOCKS 40 EVIDENCE DOWNTOWN ST3001 MySQL Tutorial 1 - University of Dublin, Trinity College Rela.onal Database Structure A Rela.onal Database can be thought of like a Filing Cabinet Tables Drawers Rows File Folders Columns/Fields Sheets of Paper Data Values Words on the Paper 10

Graph Database Uses a graph structure with: Nodes Edges Proper.es Graph databases treat the rela.onship between things as equally important to the things themselves. En.ty Rela.

11 Graph Database Uses a graph structure with: Nodes Edges Proper.es Graph databases treat the rela.onship between things as equally important to the things themselves. En.ty Rela.onship Diagrams An abstract and conceptual representa.on of informa.on Used to produce a Conceptual Schema of a Database In simpler terms, it is used to iden.fy the requirements for, and support the design of a database Describes the type of informa.on that is to be stored in the database 11

12 En..es, Rela.onships and Aeributes An en4ty is a business object that represents a group, or category of data. Do we know a similar concept? Each en.ty represents a table in the database A rela4onship captures how two or more en..es are related to one another. An a6ribute is a sub- group of informa.on within an en.ty. Do we know a similar concept? Each aeribute represents a column in a the table Rela.onship Proper.es Rela.onship Link Phrase Rela.onship Par.cipa.on Mandatory Op.onal Rela.onship Cardinality Many- to- Many One- to- Many One- to- One Recursive 12

13 Link Phrase Provides a short descrip.on of the nature of the rela.onship It is always read clockwise with respect to the en..es that it links Mandatory Rela.onships 13

14 Op.onal Rela.onships Mixed Par.cipa.on 14

15 One to One Many to Many 15

16 One to Many Recursive 16

17 Many- to- Many Rela.onships Many- to- many rela.onships are difficult to encode in a rela.onal database They should be avoided where possible. We can resolve a many- to- many rela.onship by: Dividing it into two one- to- many rela.onships. Using a linking table Many- to- Many Rela.onships Think of the following example: Try to represent this using two tables and their aeributes We have a problem 17

18 Many- to- Many Rela.onships We need a linking table: These types of rela.onships must be broken into mul.ple one- to- many rela.onships. This allows the data to be modelled correctly in the database Examples A customer can rent many DVDs from the LotsoVision store. Each of LotsoVision s DVDs can be rented to many customers An airline company flies many flights, but each flight is flown by only one airline The Globex Corpora.on operates many factories. Each of these factories is located in a region. Each region can more than one Globex factory. Each factory employs many employees, but each of these employees is employed by only one factory. 18

19 Data Types Character char varchar text Date and Time Date Time.mestamp Number bit integer real numeric Others blob boolean DBMS Database Management System Goal of a DBMS is to simplify the storage of, and access to data DBMS support: Defini.on Manipula.on Querying 19

20 Well known DBMS: Proprietary Oracle Access (Microsoa) SQL Server (Microsoa) DB2 (IBM) Open Source MySQL SQLite PostgreSQL DBMS Database Languages Programming languages which are used to Define a database (i.e. its en..es and the rela.onships between them) Manipulate its content (i.e. insert new data and update or delete exis.ng data) Conduct queries (i.e. request informa.on based upon defined criteria). The Structured Query Language (SQL) is the most commonly used language for Rela.onal Databases Supported by all rela.onal DBMSs and is a standard. 20

21 SQL SQL is split into four sets of commands which are divided based upon the tasks they are used for: Data Defini.on Language Data Modifica.on Language Data Query Language Data Control Language Data Defini.on Language SQL uses a collec.on of impera.ve verbs whose effect is to modify the schema of the database Can be used to add, change or delete defini.ons of tables or other objects. These statements can be freely mixed with other SQL statements so the DDL is not truly a separate language. 21

22 Data Defini.on Language CREATE Statement This Statement is used for crea.ng the database and its objects ALTER Statement This Statement is used for modifying the database and its objects DROP Statement This Statement is used for dele.ng the database and its objects TRUNCATE Statement This Statement is used to delete the data available in a table in a Row- By- Row manner but with out disturbing its structure Data Manipula.on Language The data manipula.on language comprises the SQL data change statements Modifies stored data Does NOT modify the schema or database objects This is always the responsibility of the Data Defini.on Language Used for inser.ng, dele.ng and upda.ng data in the tables of a database 22

23 Data Manipula.on Language INSERT Statement This statement is used for inser.ng data into a table DELETE Statement This statement is used to delete data from a table that matches certain criteria UPDATE Statement This statement is used to update data in a table that matches certain criteria Data Query Language The data query language allows users of a database to formulate requests and generate reports There is one primary command used in SQL to query the database - the SELECT Statement This statement is used to query or retrieve data from a table in the database. A query may retrieve informa.on from specified columns or from all of the columns in the table A query may have specified criteria that must be met in order for data to be returned 23

24 SQL Statement Entered SELECT location FROM department; Statement is sent to Database Returned Data is Displayed Location Tower 221 The Docks City Centre Downtown Result Data is Returned ST3001 MySQL Tutorial 1 - University of Dublin, Trinity College 24

CS2 Current Technologies Lecture 2: SQL Programming Basics

T E H U N I V E R S I T Y O H F R G E D I N B U CS2 Current Technologies Lecture 2: SQL Programming Basics Dr Chris Walton (cdw@dcs.ed.ac.uk) 4 February 2002 The SQL Language 1 Structured Query Language