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How are the different relations in a relational database tied together?
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∙ 9y ago
There must be at least one common field in the tables that are related. In simple terms you find a value in that field in one table and then find the corresponding value for that field in another. At least one of them will be unique, like in a one to many relationship. One the one table, that value can appear only once in the table. On the many table it can appear more than once. In a one to one relationship, each can only appear once in each table in the relationship. In a many to many relationship, an intermediate table is set up and two other tables are joined to it.
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All types of keys in database?
* Alternate key - An alternate key is any candidate key which is not selected to be the primary key * Candidate key - A candidate key is a field or combination of fields that can act as a primary key field for that table to uniquely identify each record in that table. * Compound key - compound key (also called a composite key or concatenated key) is a key that consists of 2 or more attributes. * Primary key - a primary key is a value that can be used to identify a unique row in a table. Attributes are associated with it. Examples of primary keys are Social Security numbers (associated to a specific person) or ISBNs (associated to a specific book). In the relational model of data, a primary key is a candidate key chosen as the main method of uniquely identifying a tuple in a relation. * Superkey - A superkey is defined in the relational model as a set of attributes of a relation variable (relvar) for which it holds that in all relations assigned to that variable there are no two distinct tuples (rows) that have the same values for the attributes in this set. Equivalently a superkey can also be defined as a set of attributes of a relvar upon which all attributes of the relvar are functionally dependent. * Foreign key - a foreign key (FK) is a field or group of fields in a database record that points to a key field or group of fields forming a key of another database record in some (usually different) table. Usually a foreign key in one table refers to the primary key (PK) of another table. This way references can be made to link information together and it is an essential part of database normalization
What does database mean in HTML?
There is no database tag per say in HTML. HTML is a markup language which simply means it's a way of formatting contents on a webpage. A database is a data structure that is used to house information so it can be called upon at a later time. In order to connect a database to some form of HTML, you'd need to have the database stored on the webserver and then access that database through a server side language like PHP which can orient the contents into HTML tags and be placed within your webpage. Basically, you'd need to use a programming language of some sort to bring together a database and HTML; it's not possible simply by typing in HTML tags. Sorry...
Is it easy to do a rent-to-own database?
It really does depend on your level of computer programming knowledge. If you have none then yes, it will prove to be rather cumbersome if you tried to create one. There are 2 most commonly used methods:-1. Database and Front-End applicationIt's important to realise that most computer database applications are comprised of multiple applications. What this means is that a rent-to-own database would comprise of a database that is held inside SQL Server or Oracle and then a front-end application that is used to view and edit the data in the database. In order to use this technique, you really do need programming skills.2. An Alternative ApproachA second way of doing this is to use a tool like Microsoft Access to create the database. This allows you to create forms for your database rather easily and by reading the help file, a person could learn what is required to put their database together.
What is the difference between a Database and a Data Structure?
A data structure is the internal representation of the data. It may be a list, a linked list, a stack, heap or just about anything else that can be immagined and represented internal to the machine. For example, the data structure may be a linked list of control blocks for a specific product that is progressing through an automated machining facility. The control block may include information regarding the product, the tolerances, date/time that the product entered the different machining centers and the inspectors who verified the product at different points along the way. The data structure (control block) may or may not be stored in a database during the manufacturing process. Some application engineers may determine that the data needs to remain in memory to address real-time issues and for speed concerns. On the other hand, the data may be handed off to a database application for archiving. A well defined database links the similar data elements together and provides lookup "keys" that allow subsequent users to view and manipulate the data.
When with different views and expertise are working together they may disagree about the best way forward identify five different skills or approaches that might help resolve conflict?
when people with different views and expertise are working together they may disagree about the best way forward.Identify five different skills or approaches that might help resolve conflict.
What is the relational database?
Relational database: Relational database means a collection data stored in different tables and each table are linked together by using primary key and foreign key. In relational database, data can be accessed from one table to another without reorganising the required table. The relational database was invented by E. F. Codd at IBM in 1970.
How do relational databases use indexes?
The index between relations databases is the common thread which ties them together. So if you have a column in each database called 'idnum' and IDNUM:001 in the first database corresponds with data in IDNUM:001 in the second database, the two databases are relational and IDNUM is their index.
What are the Advantages and disadvantages of relational data base model?
Some of the advantages of relational databases include the ability to link information about a particular person who is in several databases together by simple links. One disadvantage is that once the database is created it is not changed easily so any database forming as part of a relational database must be very carefully planed before anything else can be done
What is relational wedge?
A relational wedge is used to assess the different ways that strangers interact with each other. People are giving a relational wedge so that that they must work together in order to solve a problem.
What are the typical benefits of relational databases?
With a relational database, you can quickly compare information because of the arrangement of data in columns.A typical relational database has anywhere from 10 to more than 1,000 tables. Each table contains a column or columns that other tables can key on to gather information from that table.By storing this information in another table, the database can create a single small table with the locations that can then be used for a variety of purposes by other tables in the database. A typical large database, like the one a big Web site, such as the police would have, will contain hundreds or thousands of tables like this all used together to quickly find the exact information needed at any given time
Why is ms access called relational database?
It has the ability to set up relational databases. In very simple terms, that means different tables can be connected together through relationships. You could have a table of members of staff and a table of the names of the departments in the company they work in. Then you could make a connection between each member of staff and the details of the department they work in. Why and how you do this and its advantages can take a lot of explanation. You can do a course on relational databases, such is the amount of detail involved, so it is not simple to give a full explanation here. It would also be important to be able to demonstrate it, which cannot be done in an answer like this.
What are typical benefit of relational databases?
With a relational database, you can quickly compare information because of the arrangement of data in columns.A typical relational database has anywhere from 10 to more than 1,000 tables. Each table contains a column or columns that other tables can key on to gather information from that table.By storing this information in another table, the database can create a single small table with the locations that can then be used for a variety of purposes by other tables in the database. A typical large database, like the one a big Web site, such as the police would have, will contain hundreds or thousands of tables like this all used together to quickly find the exact information needed at any given time
What is the importance of relational database?
Relational databases provide a structured way to store and organize data, making it easier to query and retrieve information. They ensure data integrity through relationships between tables, enabling efficient data management and analysis. Relational databases also support transactions and ACID properties, ensuring data remains consistent and reliable.
Do keyfields link data together in a database?
Yes, keyfields are used to link data together in a database. Keyfields are unique identifiers for each record in a table and are used to establish relationships between tables by matching values between keyfields in different tables. This linking of data through keyfields enables the database to efficiently retrieve and manage related information.
What a tuple in a relational model?
A row of a table in relational model is known as tuple - is the easy answer. A tuple is a collection of elements that relate to one another : T = R(e1, e2, ... , en). One can view a collection of similar relations, R, as a table, where the elements of same category are projected underneath one another, and ordered as is suited for the table view. When implementing a relational database, the tuples can be spread all over in a way that suits those that make the storage system, and enables fast retrieval and manipulation of them. So, unless you specify the sorting - "Collating Sequence" of the table, you can expect a new ordering every time you view the table. The elements in the relations are bound together in the same way as rows in a table - but some relations may have more elements - "columns" and really belong to other tables - but is "projected" into the view you see as a table.
1 What are object-oriented databases and how do they differ from relational databases?
First of all, they may or may not differ. An object oriented database is a database you program by the use of small pieces, that, put together form an object. These objects can then be combined with other objects and/or be used separately. Actually, if you where to remove 'on leg' of the database that leg should be able to stand on its own. So goes the therory anyway. One relational database that has some benefits as an object oriented database is 4D. However, the stuff that one 'leg' can entirly support itself isn't actually true, however the objects are there and they do make a lot of sense. Am I making sense? --
History of rdbms?
1970 - In 1970, Edgar Codd, an IBM computer scientist, wrote a number of papers which developed the idea of a new form of relational database which went beyond the then current hierarchical and network database models. Codd's paper was instrumental in the development of IBM's prototype relational database known as System R (and ultimately in the development of IBM's DB2 database), as well as Oracle, the first commercial relational database1979 - Later in 1979, it was renamed Relational Software Inc and finally it was renamed Oracle. Prior to this Ellison was inspired by the paper written by Edgar F.("Ted") Codd on relational database systems named "A Relational Model of Data for Large Shared Data Banks. Ellison and his partners won a two-year contract to construct a relational database management system (RDBMS) for the CIA with project's code name: ORACLE. Starting with eight employees and with revenue lessJan 5, 1989 - When it can keep track of information in two or more lists simultaneously, it is a relational database. ... A relational database program would allow you to print reports or view on-screen data displays and entry forms combining elements of information from any of those listsOct 3, 1993 - Today, we also have relational databases for the masses, a new genre priced for imminent arrival on your desktop-accompanied by the resounding "thud" that ... The first blow came in November 1992 when Microsoft CorpDec 1995 - Illustra's objective was to revolutionize database management technology through a marriage of object-based and relational database management systems. By December 1995, Illustra was well on the way toward accomplishing that objective. Its technology, developed by Dr. Stonebraker, a professor of the University of California Berkeley, represented the first breakthrough in the 25-year history of the relational database.Dec 1995 - Illustra's objective was to revolutionize database management technology through a marriage of object-based and relational database management systems. By December 1995, Illustra was well on the way toward accomplishing that objective. Its technology, developed by Dr. Stonebraker, a professor of the University of California Berkeley, represented the first breakthrough in the 25-year history of the relational databaseDec 3, 1996 - 56. On December 3, 1996, Informix issued a press release announcing the shipment of its next generation database software product, the Universal Server. The Company's release stated in pertinent part: Informix Software, Inc., (NASDAQ: IFMAX), the leading provider of object-relational database technology, today announced the on-time availability of INFORMIX-Universal Server, the industry's leading open, completely integrated object-relational database management systemNov 29, 1999 - "The component model for XML is complex enough that to store it in a relational database isn't practical," Hoag says. "In the relational-database world, you have to worry about foreign key references, the depth of the model. There is a lot more complexity in mapping an XML componentFeb 1, 2002 - The Accenture system also creates a threat index, using massive computing power and relational database software. ... system designed to instantly pull together every passenger's travel history and living arrangements, plus a wealth of other personal and demographic informationAug 2, 2004 - As a Java-only database, it does not compete directly against mainstream relational database servers, such as DB2, Oracle or Microsoft's SQL Server, ... Cloudscape was developed in the mid-1990s as a relational database created specifically to work with the Java programming language.written by syed fatehyab ahmed
