The Database Concept and the Database Management System (DBMS) Databases

Activity 1 On your whiteboards, write down anything that comes to mind when thinking about ‘databases’. 5 minutes

The Database Concept and the DBMS Introduction In this topic we will be looking at databases. “A database is a persistent organised store of related data on a computer system” Persistent means that it is stored in secondary storage for later access. Organised means that as data is written to the database it is done in a particular order – this makes accessing (querying) specific data much faster and more efficient. Learning Objectives: (a)Describe a database as a persistent organised store of data (b)Explain the use of data handling software to create, maintain and interrogate a database (c)Describe how a DBMS allows the separation of data from applications and why this is desirable (d)Describe the principal features of a DBMS and how they can be used to create customised data handling applications

The Database Concept and the DBMS A simple ‘Flat File’ database + Terminology Learning Objectives: (a)Describe a database as a persistent organised store of data (b)Explain the use of data handling software to create, maintain and interrogate a database (c)Describe how a DBMS allows the separation of data from applications and why this is desirable (d)Describe the principal features of a DBMS and how they can be used to create customised data handling applications Record Field Field Name NameMeaningExamples Table A collection of data relevant to one type of entity A table of information about students Records Collection of all the data on a single entity 001, John, Doe, 12/03/1992, 7S Field Single column of data in a table John Benjamin Alex Ahmed Crystal Simon Field Name The name given to the fieldFirst Name

The Database Concept and the DBMS Entity and Attributes – More DB Terminology When dealing with databases we often talk about entities and attributes. An entity is something in the real world that we store data about. A person, a car, an order or an exam subject are all examples of entities. An entity becomes a table in a database. One instance of an entity in a database is a record. An attribute is a characteristic of an entity. It becomes a field in a database. For example, if the entity was a person, an attribute might be their surname. Learning Objectives: (a)Describe a database as a persistent organised store of data (b)Explain the use of data handling software to create, maintain and interrogate a database (c)Describe how a DBMS allows the separation of data from applications and why this is desirable (d)Describe the principal features of a DBMS and how they can be used to create customised data handling applications Record Field Field Name

The Database Concept and the DBMS Data Handling Software A database on its own is pretty useless. For a database to have any real use, there needs to be software to bring the database to life. This software might be a dedicated ‘data processing’ program used to access customer details. Or it could be, for example, a ‘computer game’ which needs to update the game’s high score table. Either way, software needs to accompany a database to enable the database to be created and data in it retrieved, updated and deleted (CRUD). Learning Objectives: (a)Describe a database as a persistent organised store of data (b)Explain the use of data handling software to create, maintain and interrogate a database (c)Describe how a DBMS allows the separation of data from applications and why this is desirable (d)Describe the principal features of a DBMS and how they can be used to create customised data handling applications

The Database Concept and the DBMS DBMS In fact, applications that access databases will all do so using a special ‘intermediate program’ called a Database Management System (DBMS). The aim of a DBMS is to isolate the database from the application(s) that use the database so that they are not intertwined as one entity. Learning Objectives: (a)Describe a database as a persistent organised store of data (b)Explain the use of data handling software to create, maintain and interrogate a database (c)Describe how a DBMS allows the separation of data from applications and why this is desirable (d)Describe the principal features of a DBMS and how they can be used to create customised data handling applications

The Database Concept and the DBMS Why is a DBMS needed? The reasons for the need to separate the database from the program are as follows: 1.The DBMS can be thought of as a guardian of the data and any application that needs to access the data has to do so through the guardian, which prevents applications from handling the data wrongly, putting the integrity of the database at risk. 2.It also means that if the code of programs are edited, programmers don’t need to worry about compromising the data as it is stored elsewhere. Learning Objectives: (a)Describe a database as a persistent organised store of data (b)Explain the use of data handling software to create, maintain and interrogate a database (c)Describe how a DBMS allows the separation of data from applications and why this is desirable (d)Describe the principal features of a DBMS and how they can be used to create customised data handling applications

The Database Concept and the DBMS Features of a DBMS It enables several different programs to access the database at one time. It provides security ensuing that only the correct people can access the data. In the event of a disaster it can back up and recover data. It supports a query language, used to retrieve, add and alter data and change the database structure. It can implement ‘referential integrity’. This stops any ability to damage relationships between tables. For example, deleting a product would not be possible if a customer was linked to the product. It controls ‘concurrency’. Which simple means that two people can work with the database at the same time – yet preventing people from overwriting each others work at the same time. Learning Objectives: (a)Describe a database as a persistent organised store of data (b)Explain the use of data handling software to create, maintain and interrogate a database (c)Describe how a DBMS allows the separation of data from applications and why this is desirable (d)Describe the principal features of a DBMS and how they can be used to create customised data handling applications

The Database Concept and the DBMS Features of a DBMS As said on the previous slide, DBMS supports a query language and this is one of the most important features. A query language is basically the commands that an application will use to ‘talk to’ a database. An application will use a query language (often SQL) to ‘Create’, ‘Retrieve’, ‘Update’ and ‘Delete’ data. And when it comes to ‘Retrieving’ data, an application is really ‘Querying’ the database. ‘Querying’ a database means ‘asking it questions’ to find the required data and this is at the heart of ‘working with databases’. This will be explored over the next few lessons. Learning Objectives: (a)Describe a database as a persistent organised store of data (b)Explain the use of data handling software to create, maintain and interrogate a database (c)Describe how a DBMS allows the separation of data from applications and why this is desirable (d)Describe the principal features of a DBMS and how they can be used to create customised data handling applications

Activity 2 45 minutes Create an A4 revision sheet which introduces the topic of ‘Databases’. The revision aid must include the following information: Definition of a Database (including the key words ‘persistent’ and ‘organised’). An example of a database table which demonstrates key database terminology (fields, records, tables, etc.) A clear explanation of the difference between an entity and a database table. And the difference between an attribute and a database field. A description of what a DBMS is. An explanation as to why a DBMS is needed. Key features of a DBMS. An explanation of what a ‘Query’ is.