Database Management Systems (DBMS) Data Handling Software Database Management Systems (DBMS)

Paper Databases A database is a collection of data or information which is held together in an organised or logical way.  Databases can either be paper based or computerised.

Computerised Databases You will come across computerised databases in every aspect of your life. Here are some examples with which you will be familiar: Search engines e.g. Google, Ask, Bing School electronic registers Library database Shop stock control system DVLC - stores details of all driver licences and car registrations

Specification Candidates should be able to define a database as a large collection of data items and links between them, structured in such a way that allows it to be accessed by a number of different applications programs.

What You Need to Learn From This Lesson Definition of a database Advantages and disadvantages of a database approach over flat files Database security Hierarchy of passwords Storage of data separate to programs

Key Words Fields Table Primary Key Record Relational Database Management System (RDMS) Query Report

Table Fields Field Names

Primary Key

Definition of files, records and fields A file is a set of related records e.g. a file of patients A record is a collection of data about a particular person, object or concept e.g. the data about one patient A field is a subdivision of a record which holds a particular item of data with a given data type e.g. Medicine quantity (data type is number) Patient name (data type is text) Primary Key field(s) to uniquely identify a record

Records

Primary Key

A TABLE is made up of RECORDS RECORDS are made up of FIELDS FIELDS are made up of CHARACTERS

File, records & fields Stock File Stock code: SP2544 Stock name: Timber door panel Material: Pine Size: 600x600mm Quantity: 25 Stock code: RF4237 Stock name: Timber door panel Material: Pine Size: 600x600mm Quantity: 25 Stock code: PY3746 Stock name: Timber door panel Material: Pine Size: 600x600mm Quantity: 25 One stock record Stock code: TM1253 Stock name: Timber door panel Material: Pine Size: 600x600mm Quantity: 25 One field

Databases & Database management software (DBMS) A database is a collection of tables and records DBMS - database (management) software Is a layer of software inserted between the different applications (programs) and this data. It is responsible for the creation/maintenance/manipulation of the database

Flat File Databases A flat-file database is a simple database that stores all data in a single table in one file A flat-file database can be stored in a text file, such as a a Spreadsheet, or in a database file that contains one or more unrelated tables.

Flat File Advantages Useful for simple lists: Easy to create

Flat File Disadvantages Large amounts of duplicated data Difficult to update If entries change all instances have to be updated Security All users have access to the same set of data

Relational Databases The problems associated with flat files can be solved by moving some of the data out of the main table and accessing it when required holds data in many tables of records which are linked by relationships. A relationship is implemented through common fields held in the two tables What's the problem?

Relational Database Advantages Avoids data duplication (redundancy) data stored once linked by key fields all data available via relational links in key fields Ensures consistency of data of data to all users

Relational Database Advantages continued Increased security - What makes databases secure? Hierarchy of passwords ID Authentication Authorisation to files and processing DBMS can check permissions Read only Write only etc. Users only allowed to view the data they are entitled to, so there is less risk of accidental or deliberate destruction. Data integrity It is possible to specify constraints on the data to ensure it is in the correct format and range.

Disadvantages of relational database vs. flat files More complicated to design and create a relational database than a flat file system More expensive because flat file system can by created simply using spreadsheet software where as a relational database needs to be created with a DBMS

Database Security DBMS controls security access to different parts of the database Each user is given appropriate access rights to the database appropriate to the type of user they are and their job

Searching for data with specific criteria. Database Software Features – Ability to: Produce Queries Searching for data with specific criteria. e.g.: looking for customers who all live in a certain postcode to arrange delivery of shopping. Produce Reports Outputting information in a printed format. e.g.: Printing customer bills with data from the customer accounts. Import/Export Transferring data between software packages e.g.: Mail merge where data is exported from

Advantages/disadvantages of Database Software Advantages of Relational Databases Disadvantages of Relational Databases Only have to enter data once They are complex, difficult, and time-consuming to design Files and tables are linked, and so means if the data is changed in one application, the rest of the database will automatically be updated for other applications Damage to database affects virtually all of the application programmes It is quick and easy to access information Search criteria can be use, saved and modified Initial training for programmers and users is needed and can be costly Everyone uses the same data, and so the data is consistent Validation checks can be performed Ensures data integrity The structure of the database can easily be changed

Database Software A database is an organised collection of data or information. Computerised databases can import or export information. This needs to be done easily as different systems are often used and the data must be read the same each time.

Query The whole point in storing data in a database is the fact that it is easy to perform searches to extract data. One way of searching for that data would be performing a search using the tables in the database. Another is using commands written in a language called Structured Query Language (SQL).

Reports Databases can perform queries and produce the results in a report. This is usually printed out and presented in such a way that it is easily understood – for e.g. graphs, charts, tables, etc.