Database Management Review Essay Sample

10 October 2017

• Datas are natural facts. Information is the consequence of treating informations to uncover their significance. Accurate. relavant and timely information is the key to good determination devising and good determination devising is the key to organisational endurance in a planetary environment

• Datas are normally stored in a database. To implement a database and pull off its contents you need a database direction system ( DBMS ) . DBMS serves as an mediator between the user and the database. The database contains the information you have collected & amp ; “data about data” metadata.

• Database design defines the database construction. A well-designed database facilitates informations direction and generates accurate and valuable information. A ill designed database can take to bad determination devising and bad determination devising can take to the failure of an organisation.

• Databases can be classified harmonizing to the figure of users supported. where the informations are located. the type of informations stored. the intended information use and the grade to which the informations are structured.

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• Databases evolved from manual and so computerized file systems. In a file system. informations are stored in independent files. each necessitating its ain informations direction plans. Although this method of informations direction is mostly out-moded. understanding its features makes database design easier to grok.

• Some restrictions of file system informations direction are that it requires extended scheduling. system disposal can be complex and hard. doing alterations to bing constructions is hard and security characteristics are likely to be unequal. Besides. independent files tend to incorporate excess informations. taking to jobs of structural and informations dependance.

• Database direction systems were developed to turn to the file system’s built-in failings. Rather than lodging informations in independent files. a DBMS presents the database to the terminal user as a individual information depository. This agreement promotes informations sharing. therefore extinguishing the possible job of islands of information. In add-on. the DBMS enforces data unity. eliminates redundancy. and promotes informations security.

REVIEW QUESTIONS

1. define each of the undermentioned footings:
A ) Data: natural facts such as telephone figure. birth day of the month. client name. Datas have small significance unless they have been organized in some logical mode. B ) Field: a character or group of characters ( alphabetic or numeral ) that has a specific significance. a field is used to specify and hive away informations. C ) Record: a logically connected set of one or more Fieldss that describes a individual. topographic point. or thing. For eg. The Fieldss that constitute a client record might dwell of the customer’s name. reference. phone figure. day of the month of birth. recognition bound and unpaid balance. D ) File: A aggregation of related records. For illustration. a file might incorporate informations about the pupils presently enrolled at Bond University.

2. What is Data redundancy. and which features of the file system can take to it? Data redundancy is when the same informations are stored unnecessarily at different topographic points. Poor informations security. information incompatibility. information anomalousnesss ( when non all the needed alterations in the redundant informations rare made successfully ) .

3. What is data independency and why is it missing in the file systems? Data independency exists when you can alter the informations storage features without impacting the program’s ability to entree the information. Missing in the file system as most informations relies on other informations

4. What is a DBMS and what are its maps?
A database direction system ( DBMS ) is a aggregation of plans that manages the database construction and controls entree to the informations stored in the database. In a sense. a database resembles a really good organized electronic filing cabinet in which powerful package ( the DBMS ) helps pull off the cabinet’s contents. DBMS maps include informations dictionary direction ( look up the required informations constituent constructions and relationships ) . Data storage direction. Data transmutation and presentation. security direction. multiuser entree control. backup and recovery direction. informations unity direction ( truth and consistence of informations ) . database entree linguistic communications and application scheduling interfaces ( Query linguistic communication where users specify what must be done without holding to stipulate how ) and Database communicating interfaces ( accessing via different webs ) .

5. What is structural independency and why is it of import? Structural independency exists when you can alter the file construction without impacting the application’s ability to entree the information. Because the file system application plans are affected by alterations in the file construction. they exhibit structural dependance.

6. What is the function of a DBMS and what are its advantages and disadvantages? It serves as the mediator between the user and the database and the database construction itself is stored as a aggregation of files and the lone manner to entree the information in those files is through the DBMS. Advantages: Improved informations sharing. improved informations security. minimized information incompatibility. improved data entree. improved decision-making. increased end-user productiveness. Disadvantages: Increased costs. direction complexness. keeping currency. seller dependance. frequent upgrade/replacement rhythms.

7. List and depict the different types of databases.
• Single-user database supports merely one user at a clip • Multi-user database supports multiple users at the same clip • Enterprise databases used by the full organisation • Centralized database supports informations located at a individual site. • Distributed database supports informations distributed across several different sites • General-purpose databases contain a broad assortment of informations used in multi subjects eg. Census and demographic informations • Discipline-specific databases contain informations focused on a specific capable country. • Operation database besides known as Online transactional processing ( OLTP ) . transactional or production database supports a company’s daily operations. • Analytic databases focuses chiefly on hive awaying historical informations and concern prosodies used entirely for tactical or strategic determination devising. It consists of a Data warehouse is a specialised database that shops informations in a format optimized for determination support and an Online analytical processing ( OLAP ) is a set of tools that work together to supply an advanced information analysis environment for recovering. processing and patterning informations fro m the information warehouse. Business intelligence describes a comprehensive attack to gaining control and procedure concern informations. 8. What are the chief constituents of a database system?

Hardware package. Peoples. processs and Data.

9. What are metadata?
Datas about informations

10. Explain why database design is of import?
Database design refers to the activities that focus on the design of the database construction that will be used to hive away and pull off end-user informations. A database that meets all user demands does non merely go on: its construction must be designed carefully. In fact. a database design is such a important facet of working with databases.

11. What are the possible costs of implementing a database system? Sophisticated hardware and package. trained forces developing. licensingm and ordinance conformity costs vendor dependance – sellers are less likely to offer pricing point advantages to bing client and updating of hardware and package ; extra preparation

12. Use illustrations to compare and contrast unstructured and construction informations. Which type is more prevailing in a typical concern environment? Unstructured informations are informations that exist in their original ( natural ) province. that is. in the format which they were collected and does non impart itself to the processing that yields information. Structured informations are the consequence of data format unstructured informations to ease storage. usage and the coevals of information. An bill. If one were to take an bill and merely scan it into a in writing. it would be unstructured informations. In contrast. if it were processed and put into a database ( later becomming structured informations ) . employees could finally happen the monthly norms. sum owed. etc. from assorted bills. While both are prevelant. I would believe semistructed informations would be the most common in a typical concern. Some information is stored but non processed ( unstructured informations such as memos ) . and some others are stored in databases ( such as bills ) but most informations are merely processed to a certain extent that is displayed in a prearranged format but non able to give all of the information contained within.

13. What are some basic database maps that a spreadsheet can non execute? spreadsheets do non back up basic functionality such as: support for self-documentation through metadata enforcement of informations types or spheres to guarantee consistence of informations within a column. defined relationships among tabular arraies. or contraints to guarantee consistence of informations across related tabular arraies.

14. What common jobs does a aggregation of spreadsheets created by terminal users portion wit hthe typical file system? Common jobs with utilizing both a aggregation of spreadsheets created by terminal users and the typical file system include: drawn-out development times. trouble of acquiring speedy replies. . complex system disposal. deficiency of security and limited informations sharing. extended scheduling

15. Explain the significance of the loss of direct. hands-on entree to concern informations that end users experienced with the coming of computerized information depositories. The loss of direct. custodies on entree to concern informations to end-users was important because it gave them the tools to change over their informations into the information they needed and pull stringsing the company data that would let them to make new information. However. it seperated end-users from informations. While this increased security. prevented redundancy and the such. it besides created a hold in which the end-user could bespeak information from the informations and when it was delivered by the DP.

Chapter 2: Datas Models

Drumhead

• A information theoretical account is an abstraction of a complex real-world informations environment. Database interior decorators use informations theoretical accounts to pass on with coders and terminal users. The basic data-modelling componenets are entities. properties. relationships and restraints. Business regulations are used to indentify and specify the basic modeling constituents within a specific real-world environment. • The hierarchal and web informations theoretical accounts were early theoretical accounts that are no longer used. but some of the constructs are found in current information theoretical accounts. • The relational theoretical account is the cureent database execution criterion. In the relational theoretical account. the terminal user perceives the information as being stored in tabular arraies. Tables are related to each other by agencies of common values in common properties. The entity relationship ( ER ) theoretical account is a popular graphical tool for informations patterning that complements the relational theoretical account.

The ER theoretical account allows database interior decorators to visually present different positions of the informations – as seen by database interior decorators. coders. and end users – and to incorporate the information into a common model. • The object-oriented informations theoretical account ( OODM ) uses objects as the basic modeling construction. Like the relational model’s entity. an object is described by its factual content. Unlike an entity. nevertheless. the object besides includes information about relationships between the facts. every bit good as relationships with other objects. therefore giving its informations more significance. • The relational theoretical account has adopted many object-oriented ( OO ) extensions to go the drawn-out relational informations theoretical account ( ERDM ) . Object-relational database direction systems ( O/R DBMS ) were developed to implement the ERDM. At this point. the OODM is mostly used in specialised technology and scientific applications. while the ERDM is chiefly geated to concern applications.

NoSQL databases are a new coevals of databases that do non utilize the relational theoretical account and are geared to back up the really specific demands of Big Data organisations. NoSQL databasesses offer distributed information shops that provide high scalability. handiness. and fault tolerance by giving informations consistence and switching the load of keeping relationships and informations unity to the plan codification. • Data mold demands are a map of different informations positions ( planetary vs. local ) and the degree of informations abstraction. The American national criterions institute criterions planning and demands commission ( ANSI/SPARC ) describes three degrees of informations abstraction: external. conceptual and internal. The 4th and lowest degree of informations abstraction. called the physical degree. is concerned entirely with physical storage methods.

REVIEW QUESTIONS

1. Discourse the importance of information theoretical accounts.
Data theoretical account is a reltively simple representation. normally graphical. of more complex real-world informations constructions. Data theoretical accounts are a great communicating toold because they facilitate interaction and communicating between the interior decorators. coders and terminal users. IN kernel it does non let one party’s prejudice toward a certain position of a information ( what they consider to be most of import ) to take clasp.

2. What is a concern regulation. and what is its intent in informations patterning? A concern regulation is a brief. precise and unambiguous description of a policy. process or rule within a specific organisation. They are of import in informations patterning because they set the phase for proper designation of entities. properties. relationships and restraints.

3. How do you interpret concern regulations into informations theoretical account constituents? You translate concern regulations into informations theoretical account constituents by following basic rules: A noun in a concern regulation will interpret into an entity in the theoretical account and a verb ( active or inactive ) tie ining nouns will interpret into a relationship among the entities.

4. What languages emerged to standardise the basic web theoretical account. and why was such standardisation of import to users and interior decorators? Data use linguistic communication ( DML ) defines the environment in which informations can be managed and is used to work with the informations in the database. Data definition linguistic communication ( DDL ) enables the database decision maker to specify the scheme constituents. They both emerged to standardise the basic information theoretical account. This standardisation was of import to both users and interior decorators because it allowed for the construct of the scheme and subschema. Schema is the conceptual organisation of the full database as viewed by the database decision maker and subscema defines the part of the database “seen” by the application plans that really produced the desired information from the informations within the database.

5. Describe the basic characteristics of the relational informations theoretical account and discourse their importance to the terminal user and the interior decorator. The basic characteristic of the relational informations theoretical account include: Hierarchal and web DBMS systems. The importance of the relational theoretical account was basically that its simpleness set the phase for echt database revolution.

6. Explain how the entity relationship ( ER ) theoretical account helped bring forth a more structured relational database design environment. The ER theoretical account helped bring forth a more structured relational database design environment because it allowed interior decorators to visually see entities. their properties and the relationships between entities. 7. See the scenario described by a statement “A client can do many payments. but each payment is made by merely one client. ” Use this scenario as the footing for entity relationship diagram ( ERD ) representation. 1: Meter

8. Why is an object said to hold greater semantic content than an entity? An object is described by its factual content and besides includes information about relationships between the facts within the object every bit good as information about its relation to other objects. Entities on the other manus. halt at being described by its factual content. The term semantic indicates intending. therefore an object evidently has more semantic content since it contains more information.

9. What is the difference between an object and a category in the object-oriented informations theoretical account ( OODM ) ? In the OODM. an object contains both informations and their relationships. Meanwhile. a category is a group of objects that portion similar objects with shared construction ( attributes ) and behaviour ( methods ) .

10. What is an ERDM and what function does it play in the modern ( production ) database environment? Extended relational informations theoretical account ( ERDM ) adds many of the OO model’s characteristics within the inherently simpler relational database construction.

11. What is a relationship and what types of relationships exist? Relationships describe associations among informations. Most relationships describe associations between two entities. When the basic informations theoretical account were introduced. three types of informations relationships were illustrated: 1: M. M: N and 1:1.

12. What is a tabular array and what function does it play in the relational theoretical account? The relational model’s foundation is a mathematical construct known as a relation. To avoid the complexness of abstract mathematical theory. you can believe of a relation. called tabular array. as a matrix composed of crossing rows and columns. Each row in a relation is called a tuple. Each column represents an property. The relational theoretical account besides describes a precise set of informations use concepts based on advanced mathematical constructs.

13. What is a relational diagram?
A relational diagram is a representation of the relational database’s entities. the properties within those entities. and the relationships between those entities.

14. What is connectivity?
The ER theoretical account uses the term connectivity to label the relationship types.

15. What is thin informations?
A instance in which the figure of table properties is really big but the figure of existent informations cases is low.

16. Define and depict the basic features of a NoSQL database NoSQL is a new coevals of database direction systems that is non based on the traditional relational database theoretical account. Features include: Not based on relational theoretical account. supports distributed database architectures. provides high scalability. high handiness and mistake tolerance. supports really big sums of sparse informations and geared toward public presentation instead than dealing consistence.

17. What is logical independency and physical independency? Logical independency is when you can alter the internal theoretical account without impacting the conceptual theoretical account. Physical independency is when you can alter the physical theoretical account without impacting the internal theoretical account.

Chapter 3: The relational database theoretical account

Drumhead

• Tables are the basic edifice blocks of a relational database. A grouping of related entities. known as an entity set is stored in a tabular array. Conceptually talking. the relational tabular array is composed of crossing rows ( tuples ) and columns. Each row represents a individual entity and each column represents the features ( properties ) of the entities. • Keys are cardinal to the usage of relational tabular arraies. Keys define functional dependences. that is. other properties are dependent on the key and can hence be found if the cardinal value is known. A key can be classified as a ace key. a campaigner key. a primary key and a secondary key and a foreign key. • Each tabular array row must hold a primary key. The primary key is an property or a combination of properties that unambiguously identifies all staying properties found in any given row. Because a primary key must be alone. no void values are allowed if entity unity is to be maintained. • Although tabular arraies are independent. they can be linked by common properties.

Therefore. the primary key of one tabular array can look as the foreign key in another tabular array to which it is linked. Referential unity dictates that the foreign key must incorporate values that match the primary key in the related tabular array or must incorporate nothings. • The relational manner supports relational algebra maps: SELECT. Undertaking and DIVIDE. A relational database performs much of the informations use work to house a information lexicon for your database. Each clip you create a new tabular array within the database. the RDBMS updates the information lexicon. thereby supplying database certification. • Once you know the rudimentss of relational database. you can concentrate on design. Good design Begins by placing appropriate entities and their properties and so the relationships among the entities. Those relationships ( 1:1. 1: M & A ; M: N ) can be presented utilizing ERDs. The usage of ERDs allows you to make and measure simple logical design. The 1: Meter relationship is most easy incorporated in a good design ; merely do certain that the primary key of the “1” is included in the tabular array of the “many” .

Review Questions

1. What is the difference between a database and a tabular array? A tabular array is perceived as a planar construction composed of rows and columns. it is besides called a relation. Where every bit. a database is more so a 3 dimensional construction that consists of many of these dealingss “tables.

2. What does it intend to state that a database displays both entity unity and referential unity? Referential unity means the status in which every mention to an entity case by another entity case is valid. Entity unity is an unity regulation which states that every tabular array must hold a primary key and that the column or columns chosen to be the primary key should be alone and non void.

3. Why are entity unity and referential unity of import in a database? They guarantee there are no information redundancy and information is non void.

4. What are the demands that two dealingss must fulfill to be considered union-compatible? When two or more tabular arraies portion the same figure of columns and when their corresponding columns portion the same or compatible spheres. they are said to be union-compatible. 5. Which relational algebra operators can be applied to a brace of tabular arraies that are non union-compatible? A natural articulation: PRODUCT. SELECT. Undertaking

6. Explain why the information lexicon is sometimes called “the database designer’s database” . Because it records the design determinations about tabular arraies and their constructions. 7. A database user manually notes that “The file contains two 100 records. each record incorporating nine Fieldss. Use appropriate relational database nomenclature to “translate” that statement. The entity contains two 100 properties. each property contains

8. A natural articulation links tabular arraies by choosing merely the rows with common values in their common property ( s ) . An equijoin links tabular arraies on the footing of an equally status that compares specified columns of each tabular array. An outer articulation matched braces would be retained and any odd values in the other tabular array would be left void.

Chapter 4: entity relationship ( ER ) Modeling

Drumhead

• The ERM uses ERDs to stand for the conceptual database as viewed by the nut user. The ERM’s chief constituents are entities. relationships and properties. The ERD includes connectivity and cardinality notations and can besides demo relationship strength. relationship engagement ( optional or compulsory ) . and the grade of relationship ( such as unary. binary or treble ) . • Connectivity describes the relationship categorization ( 1:1. 1: M. or M: N ) . Cardinality expresses the specific figure of entity happenings associated with an happening of a related entity. Connectivities and cardinalities are normally based on concern regulations. • In the ERM. an Meter: N relationship is valid at the conceptual degree. However. when implementing the ERM in a relational database. the Meter: N relationship must be mapped to a set of 1: Thousand relationships through a composite entity. • Unified Modeling Language ( UML ) category diagrams are used to stand for the inactive informations constructions in a information theoretical account. The symbols used I the UML category and ER diagrams are really similar.

The UML category diagrams can be used to picture informations theoretical accounts at the conceptual or implementation abstraction degrees. • Database interior decorators. no affair how good they can bring forth designs that conform to all applicable mold conversations are frequently forced to do design via medias. Those via medias are required when terminal users have critical transaction-speed and information demands that prevent the usage of “perfect” patterning logic and attachment to all modeling conventions. Therefore. database interior decorators must utilize their professional judgement to find how and to what extent the mold conventions are capable to alteration. To guarantee that their professional judgements are sound. database interior decorators must hold detailed and in-depth cognition of data-modeling conventions. It is besides of import to document the design procedure from get downing to stop. which helps maintain the design procedure on path and allows for easy alteration in the hereafter.

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