Characteristics And The Advantages Computer Science Essay

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Database is a collection of related data storage together, these data is structured, no harmful or unnecessary redundancy, and for different kinds of application services; Data storage independent procedures, the use of it. Insert the new data to the database, modify, and retrieval of original data can be made by common and controlled way. When a system exists in the specific database structure completely independent, the system consists of a set of database. The second definition of the database is database organization according to some data model and data collection stored in the auxiliary storage. The data collection has the following features: don't repeat, to the best way for a variety of different application the services of a specific organization, data structure is independent of use it application, data growth, delete, change and retrieval of the unified management and control software. From the development of history, database data's senior management phase of the development of the file management system.The first definition is strictly speaking, database is "according to data structure to organize, storage and management of data warehouse". In the economic management of the daily work, often need to some data "warehouse" and according to the management needs correspondingly processing. For example, the basic situation of the enterprises and institutions of the personnel department should normally be unit staff (employee Numbers, name, age, sex, place of birth, wages, recovery, etc.) are stored in the table, the table can be regarded as a database. And this "data warehouse" we need any time a trade union, salary can also inquires the number of workers in an interval, and so on. If work can be automatically in the computer, our personnel management can achieve very high level. In addition, financial management, warehouse management, production management, to create a large number of this "database", so it can use the computer to realize the finance, warehouse, production automation management.

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Answer of Question1

Primary key

A primary key, also called give priority to key in a relational database system, each record a unique key. A relational database must always have a and only a primary key. The main key is often shown as listed in a relational database table. A primary key in relational database choice often depends on administrator preferences. May change the given primary key database, the user's specific requirement changes. We need to choose an appropriate primary key, it will only mark each employee. Your first idea is to use the name of the employee. It won't work well, because it can want to see, you hired two employees of the same name. A better choice is the use of a unique employees ID number, assigned to each employee when they hired. Some organizations choose to use social security number (or similar government identifier) for this task, because each employee has a and they are guaranteed to be unique.

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Foreign Key

A foreign key, also known as the database table outside key from another table (or target) of a particular key, is usually the main key table, the use of key. The main key could be the target by many other off-balance sheets key. But the Lord Key is not necessarily a key objective.It can change the table of the primary key; change the user's specific needs. For example, when the people in the town may be the only according to their driver's license number in an application, but in another situation will be more convenient to determine them according to their phone number. When the table of the primary key is to change the, related external key Settings, if any, usually won't change. External key reference limit in two tables. Identification of the external key row or column (reference) table, refers to another (reference) set table. Listed in the reference list must be the primary key or other candidate key reference list. In a line list value must appear in a separate table references. Therefore, in the reference list does not include the value does not exist in the reference list (except maybe is NULL). This method can also be connected together of the reference information, it is important to standardized database. In the reference list quoted more than a line in the table refers to the same line. Most of the time, it reflects a (mainly table or reference list) many (sub list or reference list) relationship.

Reference and reference list may be the same table, external key reference back to the same table. This external key is a known SQL: as a self-reference or recursive foreign key in 2003. A table can have multiple external key, each external key can have different reference table. Each external key is independent of database system. Therefore, the relation table use external key cascade can be constructed.Let us suppose that department table use department name listed as the main key. Create two table, the relationship between the we add a new column employees table called department. Then we fill in the name, each staff subordinate departments. We also notice the database management system, the department staff list is a foreign key reference the department table. The database will execute reference integrity, to ensure that all the value in the department list of employees table have corresponding entries in the table of the department.

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4.0 Relationship

You have a lot of family member's relationship. For example, you and your mother is related. You only have one mother, but she may have several children. You and your brothers and sisters relationship, you may have a lot of brothers and sisters, and, of course, they will have a lot of brothers and sisters. If you get married, you and your spouse is a spouse, each other, but only once. A relational database is very similar to the relationship between their tables. There are three types of relationships:

• 1 on a: Two table only one side of the relationship in the both sides of the record. Each primary key value is only relevant (or not) in the related records in the table. They are like spouse, you may or may not get married, but if you are, you and your spouse is a spouse. Most people a relationship, forced by business rules, not naturally flow from the data. For such a rule, you can usually combine with Renee Cheng standardized rules and did not violate a table two table.

• One-to-many: The primary key table contains only a record, involves the zero, one or more than in the related table records. This relationship is similar to your parents. You only have one mother, but your mother may have several children.

• Many-to-Many: each of the two a table with the record can be any number of records in another table (or no record). For example, if you have brothers and sisters, your brothers and sisters (and there are many brothers and sisters. Many-to-many need the third table, as an assistant or a linked list is known, because relationship system cannot be directly meet relationship.

And side when you build the relationship between tables, you may be very familiar with data. Therefore, this association is more than at this point, you begin to get clear. Depends on your database system is the two table to find the value of the phase matching relation between formation. When a match is found, the system directly from two the data in the table to create a virtual record. For example, you may want to see all of the books are written by a specific author. In this case, the system will match of the books and newspapers in between the value in the table. It is important to remember that most of the time, the resulting record is dynamic, this means that their work record to a virtual often come back for any change in the bottom of the table.

5.0 Primary key &Foreign key table

This is a lecture table.Lecture id is a primary key, then lecture name is foreign key.

lecture

ID

lecture ID

lecture Name

Course

Phone number

Centre ID

1

LC1201

Kama

CICT

012-3994943

CT11001

2

LC1202

mala

DIT

012-4893834

CT11002

3

LC1203

Kenny

DIT

012-1849384

CT11003

4

LC1204

kobo

DBM

012-9384984

CT11004

5

LC1205

Kio

DHM

012-4939949

CT11005

6

LC1206

jack

CICT

012-9428948

CT11006

7

LC1207

Kit

CICT

012-4938483

CT11007

8

LC1208

Johnson

DIT

012-9384839

CT11008

9

LC1209

Kiki

DHM

012-9849348

CT11009

10

LC1210

Matt

DIT

012-9924834

CT11010

This is a student table. Student id is primary key, lecture id is foreign key.

Student

ID

Student ID

Student Name

Lecture ID

Cashier ID

Phone number

Course

4

IP092856

kooky

LC1204

CS105

016-9238339

DBM

8

IP097157

NICK

LC1908

CS208

016-3958855

DIT

3

IP110239

Jackson

LC1903

CS203

012-9846573

DIT

1

IP134787

KIMA

LC1901

CS201

013-2345678

DHM

9

IP413687

HENRY

LC1909

CS209

016-1823823

DBM

7

IP824356

NICOLE

LC1907

CS207

016-3334321

DBM

6

IP865237

SHERRY

LC1906

CS206

016-5449949

DHM

10

IP875276

KELVIN

LC1910

CS210

012-4959959

DIT

5

IP976458

JEFF

LC1905

CS205

016-2293839

DIT

2

IP981184

MATTHEW

LC1902

CS202

012-4949485

DHM

This is a cashier table.Cashier id is a primary key, student name is foreign key.

Cashier

ID

Cashier ID

Cashier name

Student Name

Course

Fees Payment

Student ID

1

CS101

HAMI

KIMI

DHM

1500

IP092856

2

CS102

hacking

MATTHEW

DBM

2000

IP098157

3

CS103

armada

BRENDON

DIT

3000

IP100239

4

CS104

acme

KEN

DBM

3500

IP135687

5

CS105

Milo

JEFF

IE100

1000

IP413587

6

CS106

sheng

SHERRY

CICT

2500

IP824356

7

CS107

alien

NICOLE

CICT

2500

IP865237

8

CS108

Xing

NICK

DIT

5000

IP874276

9

CS109

Hang

KENNY

CICT

2500

IP976456

10

CS110

Ahlen

KELVIN

DIT

5000

IP981124

This is center table. Center id is primary key, and then cashier id is a foreign key.

Centre

ID

Centre ID

Lecture Name

Course

Cashier ID

1

CT10001

kamala

CICT

CS101

2

CT10002

Milo

CAT

CS102

3

CT10003

Kenny

DIT

CS103

4

CT10004

koi

DBM

CS104

5

CT10005

nitre

IE100

CS105

6

CT10006

Jackson

CICT

CS106

7

CT10004

Michel

DHM

CS107

38

CT10005

Johnson

DIT

CS108

9

CT10006

bibs

DBM

CS109

10

CT10017

matt

DIT

CS110

6.0 Conclusion

The database can help people, database for development in our future. It will finish a series of complex data; it is easy to obtain the needed information. Computer database usually contains polymerization of data records or files, such as sales transactions, catalogue and inventory, and customer files. A database is a connected to an item of data collection, as a unit management. For example, Microsoft Access places the whole database in a data file, so an Access database can be defined as files, including data item.

Introduction Question2

DBMS A collection of programs that enables you to store, modify, and extract information from a database. There are many different types of DBMSs, ranging from small systems that run on personal to huge systems that run on mainframe.

A DBMS is usually an inherent part of a database product. On PCs, Microsoft Access is a popular example of a single- or small-group user DBMS. Microsoft's SQL Server is an example of a DBMS that serves database requests from multiple (client) users. Other popular DBMSs (these are all RDBMSs, by the way) are IBM's DB2, Oracle's line of database management products, and Sybase's products. IBM's Information Management System (IMS) was one of the first DBMSs. A DBMS may be used by or combined with transaction managers, such as IBM's Customer Information Control System (CICS). DBMSs come in many shapes and sizes. For a few hundred dollars, we can purchase a DBMS for our desktop computer. For larger computer systems, much more expensive DBMSs are required. Many mainframe-based DBMSs are leased by organizations. DBMSs of this scale are highly sophisticated and would be extremely expensive to develop from scratch. Therefore, it is cheaper for an organization to lease such a DBMS program than to develop it. Since there are a variety of DBMSs available, when a user is using the DBMS, they should know some of the basic features, as well as strengths and weaknesses, of the major types.

7.0 Answer of Question2

The main Characteristics and The Advantages of Relational Database

A relational database to store data in the form of rows and columns users understands. This series of rows and columns are called list, containing a set of table database. The main characteristics of the relational database is to create a database, based on the relational model, set algebra and other mathematical concepts and methods to deal with the data in a database. Different kinds of entities in the connection between the real world and entity relationship model. Now the models have some criticism, but it is still the traditional standard data storage. Opinion may be a subset of the data, add and simplify the multiple relations, dynamically hidden data complexity, reduce the data storage needs. A relational database using SQL, this is a simple, easy to understand language. In the plain of SQL command instructions can be realized in the form of database. Most manufacturers support database SQL standard. Flat file competitive technical supports stored in order of their data, also fail to provide user retrieval and inquire the options.Standard data query language SQL is a language based on relational database, this kind of language executive data retrieval in relational database and operation. The advantage of the relational database is basically, relational database based on set theory. Standardization is an important part of a relational database model. Relational operators, relational database support, had better have standardized table. A relational database support relational algebra, set theory to support the relational operators. In addition, from the mathematical set operation, union, intersection, extraordinary and Cartesian product, relational database also support selection, project, the relations, the connection and division operation. These actions are the only relational database.

The Main Characteristics and the Advantages of Object Relational Database

The main character is object database object relational database management system (then) is defined as an integrated database function and object-oriented programming language function of a database management system (DBMS), face database object looks like one or more existing programming language programming languages. Object reference of a permanent identifier (PID), PID can uniquely identifies a single object, may be used to set up the relations between the mark and container objects. Face is also strengthened the bag, support for inheritance. Object oriented features combination and traditional DBMS characteristics, such as lock, protection, transaction processing, query, layout of the concurrency and persistent. Then in a little more than a user's persistent memory client/server environment. Concurrent access and then can handle object, lock and affairs protection, prevent all types of threat object memory, take care of the traditional tasks, such as backup and restore like. This is so face and relational database to store different because the object, rather than form. Object relational database management system, to support object-oriented data model (hereinafter referred to as the "OO model). Object-oriented database system is a lasting, shared object library storage and management; and an object set object library is defined as an object-oriented model. Object relational database management system is a practical programming support modular design and software reuse. Program design activity focused on the connection between object and object (or communication), so as to complete the calculation. Object oriented program is the same object set (or communication). Object-oriented programming is the basic idea of packaging and scalability. The advantages of the object relation database are reuse can be extended from the database server, so that focus executive core function, not in each application code. The second advantage is an example is a complex type (or extended basic types) defined in the database, but it is the many applications. After it was asked to define this type in each application procedures, the use of it, and the development of the interface between software "type and" on behalf of the database. Sharing is because of this reuse. The advantage of the past from a practical point of view, the end user more willing to let small "leap" related to object relation, but from, must deal with a completely different paradigm (object-oriented).

The Main Characteristics and the Advantages of Object Oriented Database

Object-oriented is an understanding method, is also a new programming method. Object oriented method and database technologies together, make the database system analysis, design, maximum limit conform to the objective understanding of the world. Object-oriented database system is a database system in order to meet the new database applications need a new generation. The advantages of the object-oriented database of flexibility and simple to construct a database: view from software development prospect, the user interface between and relational database programming is flexible and friendly. At present in most products RDDMS use standard query language of SQL, and allow users to access information from a product almost no difference, another product. Interface and relational database application software have a similar program access mechanism, and provide a large number of standard data access methods. Database design and standardization process is simple, easy to understand. Strong relational database, a wide range of functions, has effectively support many database applications feel satisfied.In the object refers to the special operation bag in a set of attributes and group attributes. Inheritance of class a basic relations in a class hierarchy of different kind of associated Shared properties and operating mechanism. News is a means of communication between objects, an object sending messages to another object request it service. In addition, object-oriented data characteristic bag information hiding message polymorphism

Conclusion of Question2

In the conclusion, relational database of three kinds of classification, object-oriented database and object relation database has its own characteristics and practical. Because they give database many auxiliary. So we have to use.

8.0 Appendix

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