Monday, March 4, 2019
Database Design P1, M1 & D1 Essay
Database is a place to store lots of entropy, figure it as a giant virtual cope withing cabinet that mickle be organized in numerous ways. Theres parcel c altogethered (DBMS) which stands for informationbase management system which allows the intentr to manage entropy in selective informationbase such(prenominal) as create, delete or update.EntitiesEntities ar objects with signifi green goddesst mass and purpose, in database entities ar tabular arrays. Every t sufficient contains many a(prenominal) knit stitchs/attri barelyes. The user mustiness create a elude before in instalting any data. When creating a table you exact to define a few things, data type, cranial orbits evoke & a description.Fields NameThis is a column heading, this allow for unwrap the title for the column etc first name, last name, address.Data TypeThis is the mental object of the data & the data type decides what content understructure be arousalted & the consign size.DescriptionThis is apply to explain the content & shows a list of limitations the user lowlife change to get a more accurate practice etc. in vomit up mask.AttributesA characteristic, for example a field has many attributes such as data like numbers or letters. Attributes preempt be used as a synonym for a field. In DOS systems, each file aways has an attribute, each file has many properties that shows if the file is read scarce, visible or encrypted.QueriesA query is use for searching some specific come in. It allow user to rectify conditions and in that respectfore search the record which match the conditions. User to a fault is able to manage the search mix up with other table and sort the ordinance of the result.ReportsA Report is a summary of record. Everything you plain to print should put inside. Its purpose is for user to view information quickly and easily so display the result simply and efficiently is the main point.FormsForm is used for collect and edits information and tran sfers them to table. It is similar to application forms that allow user to fill in or delete their data easily and it also able to let user design own user interface. User throw out insert as much control as they like to physique the user interface beautifully.RelationshipsRelationship typesDatabase carnal knowledgeships are very similar in that theyre associations between tables. There are three types of transactionhipsOne-to- wizard some(prenominal) tables of the relationship have one field that matches up, for example a get hitched with couple that both have a child that has no relation to the other partner. This rarely ever haps in a business plaqueOne-to-many one-to-many is where one table has none/one or many relations with the other tables handle but the other table has only none/one field. For example, you have only one mother, but your mother may have several children.Many-to-many Both tables have one/many relations to each others fields. Usually in this instance t here are usually 3 tables.BenefitsThe benefits of having databases online are that its easier & fast to do.The amount of paper haved & room is very beneficial. Its quicker & easier for the user to find important data in the database. The user can make forms to find & read information easier. The user can fate rules to make the data input more accurate & legit. You can save the information on bigeminal storage units (hard drives) So if the information has been tampered with, theres always a spare facsimile somewhere safe. working class 2 primary(a) keyThe primary key of a relational table uniquely identifies each attribute in the table. Primary keys could be a unique attribute such as social protective covering number for a person or student etc. Primary keys may consist of a single attribute or triune attributes in combination. Primary keys connect tables together in relationshipsReferential uprightnessThere is a feature with databases called relational database management s ystems (RDBMSs) that prevents users or applications from enter inconsistent data. Most RDBMSs have referential integrity rules that you can apply when you create a relationship between two entities. For example, reflect Table B has a foreign key that points to a field in Table A. Referential integrity would prevent you from adding a record to Table B that cannot be linked to Table A. In addition, if I deleted a attribute in table A, if it is linked to table B, the data that is connecting both attributes will be deleted. This is called cascading delete. Finally, the referential integrity rules could specify that whenever you neuter the value of a linked field in Table A, all records in Table B that are linked to it will also be modified accordingly. This is called cascading update.D1 Analyse Potential Errors in the Design & crook of a Database and explain how these can be avoidedThere are many common errors that could occur while using database, its important to date how these c ommon error happen & what causes them.Deletion of records & fieldsDeleting important records & fields happen quite commonly, its caused by the user or by accident. If this does happen its always safe to know there is a copy of the data saved somewhere else in case this happens. Its inviolable to have a refresh back up time for 1 hour so every hour, the data renews itself. Human error leads to depravity or loss of fields so to ensure this doesnt happen it would be best to set administrative rights to the right users so only the right people can edit or delete fields, if the unseasonable people try to use the database, an error or password will be shown. Making more than 1 copy of the data is sharp just in case something happens to the first copy.Incorrect data typesTo decrease the chances of getting incorrect data types in database, its best to put input masks on the fields. This stops incorrect data being imputed on data forms like sign-up sheets. Its also wise to have multiple election questions & drop down menus this makes it more accurate to get correct data. exploitation drop down menus makes it easier & quicker for the user to get a unequivocal & effective data results. By using the drop down menus & multiple choice questions, it ensures correct spelling & grammar of important information.ValidationTo ensure the data is imputed clean & correct you need to use proof rules. This is done by setting rules in the design view where the user can set what data can be imputed & what is invalid. An effective tool is the limit find out where the user can set a limit to the amount of characters that can be imputed into the database. Range checks are effective to ensure etc. birthdays, it sets the month from 1-12 & has a set range to when theperson was born etc. 1950-2014 (we are currently on 2014 so I dont need to extend the range). Grammar checks are there to make sure the data isnt misspelt, it also makes personal information & letters easier to produce. Theres a rule that can be set up on database that checks the inputted data for any incorrect information, if it finds something wrong, an error message will pop up & notify the user.Null ValuesNull values is similar to validation in where the user needs to input data & there are a set of rules to ensure the user inputs the correct/legitimate data however null values are shown when no data has been inputted into a specific textbox. An error message will pop up if no data is put into a specific field, this rule is usually put on by the user as when starting database, you get a lot of blank fields. This rule is useful for fields that need data in them such as personal details, bank details etc. If the user doesnt type in anything into the textbox & clicks accept or enter an error message will pop up notifying the user about the null values. The boxes with errors are marked differently to the textboxes without errors, this is to clearly lay where the error is & makes its easier & qui cker for the user to resolve.