ITGS Databases

Databases Databases - organized collections of related data Databases Databases are at the heart of many IT systems Example: student records Databases Data is stored in an organized manner so that it can be retrieved later Business databases , transport databases Search engines - (I.e. Google) use databases to store both the contents of web pages (to enable their searches to work) and details about user’s behavior, including common searches and topics of interest

DBMS Database Management Systems (DBMS) Online databases (Wikipedia) - hold huge volumes sof articles, images and video accessible to anyone with an Internet connection Government databases Database Management Systems (DBMS) The software used to create and maintain databases Spreadsheet applications like Microsoft Excel focus on numerical calculation and are not considered database programs Database structure - organizing information into fields, records, and tables, determined by how the pieces of data relate to eachother

Database Structure Fields - smallest pieces of information in a database A property of an item Record - collection of fields that relate to the same item Table - collections of records that are all the same type Primary key, or key field - a field which is different for every record in that table, allowing each record to be uniquely identified

Structure of keys Composite key - using two separate fields together to form a composite key separately they do not uniquely identify records, but they do when combined Secondary key or alternative key or index - a field which might frequently be used to search a table. This key doesn’t have to be unique; a table can have several secondary keys Data type - determines what sort of data can be stored in each field in a database - text, numbers, a date or an image

Flat File Databases Data types are a good first step to helping ensure alidation of data by allowing only data of the desired type Flat file databases - a database which contains just one table Adequate for storing small amounts of simple data Redundant data - data that is needlessly repeated Redundant data causes several problems: Data integrity The more often data is repeated, the higher the chance that a mistake will be made

Relational Database Relationships Relational database - splits data into multiple tables, each containing records related to one type of item or entity Normalization - creating a relational database which has no redundant data Relationships Once the data has been normalized into separate tables, those tables must be linked, or related, to other tables This way, the details can be referenced from one table to another One-to-many relationship for example, one author has many books, but each book has only one author Foreign key A field which exists to be part of a relationship with another table

Queries Query - a way of selecting only the records in a database that match certain criteria Queries are essential for accessing only the required information from a database Boolean operators - mathematical operators such as greater than or less than to compare values, such as AND, OR, and NOT are used to combine criteria in a search Parameter queries Prompt the user for a value when the query is run The data entered by the user is used as the criteria for the field Forms Used to present a user friendly graphical interface for entering and altering data in a database Forms shield users from the complexity of database tables, queries and relationships

CSV and TSV CSV and TSV are common ways of transferring data between different database and spreadsheet applications Useful when programs use different file formats to store their data Both save fields and records into plain text files, which can be read by most database and spreadsheet programs Also referred to as comma or tab delimited values CSV (comma separated values) - separate each field value with a comma TSV (Tab Separated Values) - separate each value with a tab Reports A way of presenting data from a table in a database in a more professional manner than the default data sheet view Report layouts can be customized Color, data field layout, etc. Structured Query Language SQL - a language for writing instructions to manage databases

SQL Issues: Integrity Validation Designed to be easily understandable by humans Compatible across different database products Can be used to create fields, records, tables, run queries, and edit or delete information Issues: Integrity Data integrity - ensuring that data is correct, relevant and up to date - one of the biggest issues related to databases Validation The process of ensuring that data is in the correct format for a particular field For example: when a credit card number is entered, it shoul contain exactly 16 numbers Just ensures correct format, not correct data Microsoft Access - input mask allows the user to specify requirements for each character of the input

Verification Verification - checks that data is actually correct Very hard to achieve Several possible techniques: Entering data twice People enter data once, then enter it again, and the system highlights any differences between the two sets of data and requires resolution Comparing with the original documents - comparing the original paper with the data entered Verifying with the data subject - asking someone if the data is correct Issues: Privacy Data warehouses and centralized databases have allowed vast amounts of data to be collected, stored and processed Data matching - used to build up a profile of an individual by combining data bout them from several databases Data mining - discovering hidden patterns and trends in large databases

Privacy The UK has a really large DNA database UK Data Protection Act specifies how companies can collect, store and use personal data: Obtain consent State purpose of collection Distribution to 3rd parties (disclosure) Length of storage (destroy when no longer needed) Security

Security Database auditing - allows data controllers to view both successful and unsuccessful attempts to access, change or delete data in a database