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What is a database. The database is responsible for managing the data; it can be fast storage and retrieval of data application. Database information can be collected, organization, management, update and can be easily accessed. According to the database content types: a bibliography, text, data and images. The database can be divided into different types of databases are most relational database because it can store the data in tabular form table each row in the table can be kept the same information sorting. In the computer, database is organized according to their classification and the most common method is the relational database as a form of database, the database in which the data is defined so that the database can be reorganized, can be in different ways to access. Distributed database is a dispersed or reproduced at a different point in the network. An object-oriented database is the data defined in the object class and subclass data are consistent. Computer database data can include data records or documents, sales, product catalog and customer files and so on. There is also a database management can provide users to read or write access and the specified report growth and analysis ability.
A database management system is a software system can be large disk resident database creation, in a standard way for data retrieval query statues. There is a query results to efficiently retrieve and consisted of a large number of users to use the system and in the same way. Whether the system fault can be guaranteed to provide data. Database management and data is most common in the mainframe system there are small mid-range systems and distributed workstation such as the personal computers and AS/400. SQL is called structured query language is a standard language can be interactive query can also update the database is IBM DB2, Microsoft's SQL Server, Computer Associates, Sybase and database products such as Oracle.
3.0 Answer of Question 1
The database can be divided into 2 categories, primary and foreign keys. Primary key is for each table in the database record identifier. It can be a normal attribute and is guaranteed to be unique in the table everyone does not exceed more than 1 records. And it can generate DBMS social security number as a unique identifier or GUID, in Microsoft SQL Server. In addition, the primary key can also be composed of a single property or multiple attribute combination. A primary key is usually a number, text or data type. For example, the database will make the significance of computer include definitions of terms in each term lists only once in the database. Most database management systems allow the field is defined as "Unique". Records of the primary key of the DBMS provide a simple method for searching, sorting and simple access to records. Therefore, helps in multiple table related records and when a table has more fields can be defined as "Unique" also can only have a primary key for each table. In the table definition primary key is a unique and important part of. There is a table cannot have more than one primary and in the primary key column cannot contain a null value. In the database a primary key is used to identify the row unique identifier. If a student ID record, passport number as the key. Primary key can use it to perform operations can also be in a table to find the data is modified, deleted or extraction.
If the public key in a relationship is the primary key, then the public keyword is called another relation foreign key. Thus, FK represents two relations. In another relation foreign key as the keyword table is called the main table, with the foreign key table is called the main table from the table. Foreign key is also known as the foreign key. In other words, if the relationship mode of R in a R attribute set is not a primary key, but a relationship between R1 primary key is the attribute set is R foreign key relationship model in database design, usually abbreviated to FK.. A foreign key reference is to ensure data integrity. Allow only appeared in the values in a database. Foreign key also comprises a database table from another table key is to point to specific keys are usually the primary key table using. Primary key can be targeted by a number from the other table name. But the key will not necessarily is another key goal .It is possible to change the primary key in the table when it requires the user to change. Establish a foreign key, when inserted in the data test data in table whether there is, if not exists cannot be inserted, by which can improve the maintenance database consistency and integrity.
Data in the primary key constraints can also be defined on a table in a relational database; can prevent duplicate records when the user entered into the table. A primary key is the function of the database in the reference table between the two databases in the implementation, it is a foreign key can reference target. In addition, the primary key in the table is only the data in the database table ranks in the value of the one or more combination. A primary key is an important part of the entity type recognition. A good primary key from the DBMS automatically generated integer value, also have access to the data type of automatic number primary key and Oracle also has a primary sequence of objects. The primary key of the table can be divided into two types of key columns and the descriptor columns. Key column contains the information to other people, places and things. Descriptor contains information on the people, the place that can be specified by a row in a table. The primary key of the table are usually assigned to specific fields may also be included in the multiple values of similar news article database may also be used in both the title and date fields to uniquely identify each entrance and at the same time. Therefore the title and date key combination also ensure that no item has the same title in the same day.
In the foreign keys in a database is a relational table field matching columns in another table's primary key. In the foreign keys in a database can also be used for the cross reference table. Although the foreign key is also good, it will also not uniquely identifies a record in the table, they can also provide important benefit is that it will enable us to create shared fields between tables link, it can also consider the customer and the order of the table, and so on. Primary key can also be used for database systems; each record should be unique in the database. The database management system will also implement a unique key. If we try to insert a record into the table's primary key, you can copy the existing record and insert failure and so on. Most of the primary key of a database is also able to generate its own. Also known as Microsoft's software, it specifies the data type of the configuration using the number that uniquely identifies each record in a table. At the same time it is effective, this is a very bad practice, because it will give you a meaningless value in every record in the database table. The database can also enforce referential integrity Assurance Department column of the values of all the employees table can correspond to tables in the database.
In conclusion, we can get the information database, the database for computer users is very important and very helpful .Database system can help us to create database tables. In addition, the database allows users to easily understand the data. A database of all types of bonding is very helpful and very useful.
5.0 Answer Question2
The Main Characteristics and Advantages of Relational Database
Relational database is organized as a set of formal description; you can easily access data forms data collection. Relational database rows and columns of data stored in the user understand form. This series of row and column called table consisting of a group of database tables. Relational database applications can be stored and retrieved data very quickly. A relation refers to the data in the database storage and organizing mode. Storage and management of the relational database management system data is the basic form of a two-dimensional table. Relational database has important advantages are easy to extend. The relational database is the main feature that creates a database relational model and set algebra and other mathematical concepts and methods on the basis of processing the data in the database. Now the model has some criticism, but it is still the traditional data storage standard. Standard query language SQL is based on a relational database language, the language of relational database and the operation to perform data retrieval. Relational model relational data structure, relation operation set integrity constraint will consist of three parts. When you create a database, you can be in the domain of data column definition may be of value and further limitations may not apply to data values. Will relational algebra relational database support, so the set operation. In addition to set the mathematical operations: difference and Cartesian product, union, intersection, and relational databases also support project, select, and operations division.
Relational database has the advantage basically is based on set theory in relational database. Standardization is an important part of the relational database model. The relational operators, relational database support, preferably with a standardized table. Relational database to support the relational algebra, set theory support the relational operators. Relational database is one of the most popular ways to store large amounts of data. In a relational database data organization method makes it easier to understand the data user. It allows information to easily be grouped or comparison of type, such as a year or name. The relational database with a simple operation, data and retrieve user database. In addition, create database define relationships between tables so that the user can store data complete picture. A relational database has a good safety because can for database access, support, the database administrator can access based on the permissions required by the data in the database table. A relational database support users and permissions to meet the security needs of the database concept and a relational database system and provide support for distributed to achieve scalability.
The Main Characteristics and Advantages of Object Oriented Database
Object oriented database called the object database management system "object" is the object oriented method, learn new programming method. Object-oriented technology and database technology, database system analysis, design, the greatest degree of accord with the objective understanding of the world. In Java, C + +, Smalltalk and some other object-oriented languages, the use of object. Object basically includes means defined object attribute, data can be very simple, such as a string, integer and real numbers or may have a complex object attribute data attributes and methods. The object of which relates to a set of attributes and a set of attributes for professional package. This is a group with the same attributes and operations of object descriptions. Contain executable code and data object. As for other data objects, or can be from an external object to access features. As the object, by sending a message to another object, it acts as a means of communication between news .In additions, object oriented data feature pack information hiding message polymorphism. Methods cannot be stored in the database, and reusable class. In object oriented database, data navigation is similar to the model of object oriented transmission database manager defined objects and the relationship between the child .In the relational database model, data, rather than explicit operations defined objects and the relationship between the children.
Flexibility and simplicity to create objects in the database oriented advantages: from software development prospects, the user and database programming interface is the relationship between the flexible, friendly. Object oriented database system allows a given environment, as a set of objects and relationships between them is the semantic modeling. In addition, the application of the object and the relationship between them in the complex environment of usually display very complex structures, including additional properties. Relational database application software interface, a similar program access mechanism, to provide a large number of standard data access method. Database design and normalization process is simple and easy to understand. Powerful relational database, a wide range of functions, has effectively support multiple databases satisfy the application. This database system, usually based on the classical data model, they are often tailored, fairly simple entity, causing great semantic gap and more complex entity.
The Main Characteristics and Advantages of Object Relational Database
Object relational database management system is the actual programming support modular design and software reuse. Programming activities focusing on the establishment of object and the object, thus completing the required computation of contact between them. Object oriented programming is interconnected to a collection of objects. Object relational database relational database and object oriented programming function combination. This means that when developing the database, you can include the methods and data types. This will increase your ability, through the sorting, and quickly find the files in a database. By integrating these data types assigned to your document, you can better screening them through the database. You can retrieve documents that share the same characteristics. Object oriented database system is permanent shared object library storage and management personnel; but by a kind of object-oriented model definition object library collections of objects. Add new data types, access method and object oriented programming find function extended object-relational database function. You can use the alphanumeric data type to add a string of characters. Complex data types can be combined to already exist in the database data type character. You want to include text, or the number of bytes used to create it, you can specify the data type. User defined data types can be either opaque or distinctive. You can also add a user defined virtual processor.
Object relational database is the main feature of object database management system (object) is defined as a database management system (DBMS) of the object oriented programming language function integrated database function, object database object appearance or programming languages like one or more existing programming language. Object relational database can be used to generate a database management system. You can connect them to the company's Web site, to allow for such items as your inventory records are updated. These updates, click when the user through which a programming, to connect to the database management systems. He objects combination object attribute control button placement sequence and conventional DBMS functions, for example, locking, protection, transaction processing, query, concurrency and persistent layout, can make your website using component object.
Object relational database has the advantages of reuse from the extended database server, so that the core function is concentrated, execution, rather than in each application of the coding capacity. Before it was needed to use it, each application is defined in the type and development software type and it in a database that forms the interface between. Sharing is the reuse of the results. A final advantage is from the practical point of view, the end user will be more happy little leaps', from relationships to object relations, but to do a completely different model.
In conclusion, the three words in the relation database is object oriented database and object relational database has its own advantages and effectiveness. They have the database can be brought about many benefits, so we must make full use of them.