Computer Science
Databases
Databases are organized collections of data that are stored and accessed electronically. They are designed to efficiently manage, retrieve, and update large volumes of information. Databases are widely used in computer science for applications such as websites, business systems, and data analysis.
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9 Key excerpts on "Databases"
eBook - PDF- Christine Mullings, Stephanie Kenna, Marilyn Deegan, Seamus Ross, Christine Mullings, Stephanie Kenna, Marilyn Deegan, Seamus Ross(Authors)
- 2019(Publication Date)
- De Gruyter Saur(Publisher)
The term 'database' is a much abused word and is often used as shorthand for referring to the whole variety of tasks encompassed by the phrase 'database management system'. A formal definition of a database is as follows (after Martin): A collection of interrelated data stored together with a controlled redundancy to serve one or more applications in an optimal fashion; the data are stored so that they are independent of the programs which use the data; a com-mon and controlled approach is used in adding new data and modifying and retrieving existing data within the database. A more succinct definition that is more relevant to the humanities is: A database is an organized collection of useful and related facts and figures, stored in such a way as to make that data easily and efficiently retrievable and updatable. A database management system (DBMS) is the software used to handle the database. This can be something as complex as packages like IDMS or Ingres, where the software is a set of building blocks that need to be carefully designed and put together, or something as simple as dBase III+, which lacks the sophistication of the larger packages, but has immediate functionality. In this chapter the phrase 'database system' will be used to encompass both the database and the DBMS. There are eight keywords in the shorter definition which deserve further elaboration: stored, useful, organized, related, retrieved, updat-able, easily, and efficiently (see Table 1 for a summary). A database comprises useful, stored data. This implies that a database should not store data that will not be used. However, there is a reverse implication. If the required data are not in the database they cannot be used. As a consequence it is possible to suggest that if there is any doubt about whether to include or exclude some facts or figures then they should be included. It is easier to discard irrelevant data than it is to have to go back and enter a completely new set of information.
eBook - PDFTechnology for Success
Computer Concepts
- Cengage, Jennifer Campbell, Mark Ciampa, Barbara Clemens, Steven Freund(Authors)
- 2019(Publication Date)
- Cengage Learning EMEA(Publisher)
Module 13: Databases CC 13-25 13 MODULE Summary A database is a collection of data organized in a manner that allows access, retrieval, and report- ing of that data. Data is the lifeblood of most organizations, and Databases are entrusted with the critical job of organizing this data, making it easily accessible when needed, and ensuring the data is kept safe and secure. Unlike a spreadsheet, a database can show relationships between tables. A relationship shows how data in one table relates to data in another table. However, the many advan- tages of Databases come at a cost; Databases are complicated to design and set up, requiring intricate knowledge of the data in order to structure it appropriately. Relational Databases rely on relationships between types of data to show how some data is related to other data. Relational Databases are best suited to data that can be organized into tables where each record in a table stores the same pieces of information. Most relational Databases are managed using Structured Query Language (SQL). The data in a database is accessed through a database management system (DBMS), which is a collection of programs used to interact with and manage data in the database. One common example of a DBMS is Microsoft Access. Others include Oracle Database and MySQL. When you interact with your social media account on a website, you’re using the front-end database user interface that is built using web languages such as HTML, CSS, and JavaScript. Database designers and administrators interact with the database’s back-end, which includes the database server host- ing the data, some aspects of the DBMS, and the database itself. Microsoft Access includes both front-end and back-end elements. Data in a database is organized to allow for quick searches and to support connections between data in relationships.
eBook - PDF- R. A. Reynolds(Author)
- 2014(Publication Date)
- Butterworth-Heinemann(Publisher)
Chapter 5 Databases Principles The handling of large amounts of information was an early application of computers and over the years many programs were developed to deal with different categories of data. It came to be realised, however, that a single set of techniques can be used to handle almost any type of information, and by the early 1970s generalised database management systems were in common use . A database is essentially a mass of information organised so as to permit easy extraction of the items of information contained. Computers do not have to be involved: an ordinary filing system is a database, as is a dictionary, although the latter cannot be updated. To get a clearer idea of the concept of organising data, we can consider a list of clients such as would typically be used for secretarial purposes. The list might be divided into four columns, giving for each entry the client's name, address, telephone number and the name of a contact person. This list can be expressed as a tree structure having the form illustrated diagrammatically in Figure 5.1. Client 1 Client 2 Client 3 Figure 5.1 The organisation of a tabular database 63 64 Databases From a single 'root node' there is a branch to a node for each client, from which in turn there are branches to the actual items of data. This list is a rigid structure in that there are exactly four items of data for each entry and so it lends itself to being laid out in tabular form. Many of the Databases an architect will use have this form; thus a room-finishes database might have entries under columns for the room number, floor finish, wall finish and ceiling finish. Similarly, a database holding information on doors would have entries for door height, width, colour, etc. The columns are referred to in database terminology as 'fields'. Each field will have an identification name or code by which it will be referenced and will be filled with a certain type of data.
Available until 4 Dec |Learn moreInformation Systems
What Every Business Student Needs to Know
- Efrem G. Mallach(Author)
- 2015(Publication Date)
- Chapman and Hall/CRC(Publisher)
In theory an organization could develop software to do this on its own, but few if any companies have the resources. Hadoop began life as a search engine project supported by Yahoo! Today, it is supported by the open-source community. Because it is widely used, its users benefit from a support infrastructure of software, training, and expertise. Data, Databases, and Database Management ◾ 165 Where you fit in : Businesses are finding more and more value in big data as new technologies enable them to use it. Staying aware of opportunities means looking at all the data in the world around a business, not just data that people have traditionally associated with computers. DATABASE MANAGEMENT SYSTEMS By now, you have seen that Databases are complicated. Accessing data in one doesn’t have to be, though. Software packages can manage Databases so you don’t have to. Such pack-ages are called database management systems (DBMS). DBMSs are a type of system software . They are above the operating system, below users and their applications. Applications access Databases through a DBMS, as shown in Figure 5.17. It’s based on Figure 4.3, which shows where software fits in the overall scheme of a system. The DBMS accesses data via the OS, which coordinates access to storage hard-ware as a shared resource. Databases include metadata as well as data. Metadata means “data about data.” A DBMS uses metadata to access data. Metadata includes the name of a data element, so users and applications can refer to it; describes its format, such as a photo or a decimal number; and tells the DBMS where to find it. Metadata may also include access control information: who may access a data element and what each user may do with it. An application that needs data sends a message to the DBMS saying what it requires, often using Structured Query Language (SQL, sometimes pronounced “sequel”).
eBook - PDF- Klaus R. Dittrich, Andreas Geppert(Authors)
- 2000(Publication Date)
- Morgan Kaufmann(Publisher)
1 Component Database Systems: Introduction, Foundations, and Overview Andreas Geppert Klaus R. Dittrich University of Zurich • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 1.1 Introduction Database management systems (DBMSs) support individual applica-tions and comprehensive information systems with modeling and long-term reliable data storage capabilities as well as with retrieval and manipulation facilities for persistent data by multiple concurrent users or transactions. The concept of data model (most notably the relational models, Codd 1970; and the object-oriented data models, Atkinson et al. 1989; Cattell & Barry 1997), the Structured Query Language (SQL, Melton & Simon 1996), and the concept of transaction (Gray & Reuter 1992) are crucial ingredients of successful data management in current enterprises. Nowadays DBMSs are well established and are, indeed, the cornerstones of virtually every enterprise. Traditionally, data elements stored in Databases have been simply structured (e.g., employee records, and product and stock informa-tion). Transactions have been of short duration and often needed to access only a few data items. Most traditional queries have been simple and the techniques used to answer them efficiently are well under-stood. Taking a broader view, DBMS-based information systems have been built in a rather database-centric way; that is, environment deci-sions such as the use of mainframe-based or client/server architectures have been typically based on what the DBMS itself requires or supports in this respect. In the recent past, however, more and more new and demanding application domains have emerged that could also benefit from data-base technology, and new requirements have been posed to DBMSs. Many applications require the management of data types that are not handled well by conventional DBMSs.
eBook - PDFSoftware
A Technical History
- Kim W. Tracy(Author)
- 2021(Publication Date)
- ACM Books(Publisher)
These have evolved into small DBMSs such as SQLite that runs on smartphones and other smaller devices. ∙ PC Databases: Personal computer (PC) Databases were initially developed largely independently of larger system DBMSs. Databases such as FoxPro (Fox Software) and dBase (Ashton-Tate) were developed in the early 1980s and served to help in building PC applications. 226 Chapter 7 Database Management Systems ∙ Data warehousing and data warehousing machines: As the number of Databases grew in a particular organization, there was more demand to use that data together to better understand what was occurring in the organi- zation. So, data warehouses were built in varying models to support that integration of data across multiple origin Databases in order to do that type of analysis. ∙ Data mining: Data mining is a technique that grew from trying to extract interesting patterns from large datasets, such as data warehouses. There are a wide variety of techniques for doing this including statistical, visual, and machine learning-based techniques. ∙ Unstructured DBs/NoSQL: As the amount of unstructured data continued to grow with web data and traffic and the need to handle data not structured in tables, such as eXtensible Markup Language (XML), database systems were developed to handle this data. The re-emergence of non-relational Databases in the 1990s have been generically called “NoSQL” Databases, meaning they did not use SQL as their query language. Many of these now also support SQL, which has altered the meaning of NoSQL from “no SQL” to “not only SQL.” ∙ Deductive Databases: As the need to store knowledge grew, several deductive Databases were developed to be able to use logical inference to reason about the knowledge it contained. One of the most popular query languages for deductive Databases is Datalog, which uses Prolog-like syntax.
- Mark L. Gillenson, Paulraj Ponniah, Alex Kriegel, Boris M. Trukhnov, Allen G. Taylor, Gavin Powell, Frank Miller(Authors)
- 2012(Publication Date)
- Wiley(Publisher)
Microsoft SQL Server is one of the most full-featured database products on the market. It includes a wide range of features and supports something of an object-relational database model. Different versions, called editions, are available to support a wide range of database needs. A SQL Server database is physically made up of at least two and pos- sibly more files. One required file is the database file and contains the database objects and data. The other is the transaction log that tracks any activity that modifies the database. The data storage model is designed so you can create additional data files as needed and specify the physical file locations. You can then define the file in which a database object is cre- ated. This gives you a way of spreading a database across multiple hard disks. You have control over how the space is used and, by sharing the work between multiple drives, a way of improving database performance and I/O throughput. 44 INTRODUCING Databases AND DATABASE MANAGEMENT SYSTEMS The data storage component also relates to the storage of the structure defin- itions in the data dictionary, the database’s metadata. Metadata is a term referring to data about data. It’s the data that describes the database and database objects. The storage format is specific to the database management system software used. Structure definitions specify database and object schemas. In this context, schema refers to the design and structure of database objects. For example, a table’s schema describes, among other items, the columns that make up the table. Speed is of the essence for the storage devices holding the data dictionary. This is especially true because, with many database systems, the data dictionary must be accessed first before the data is accessed. You may also have removable storage media components, such as a tape drive or writeable CD or DVD drive, to support database backups and data archiving.
eBook - PDFConceptual Data Modeling and Database Design: A Fully Algorithmic Approach, Volume 1
The Shortest Advisable Path
- Christian Mancas(Author)
- 2016(Publication Date)
- Apple Academic Press(Publisher)
—Roger Bacon 19 Data was stored since the dawn of humanity on various media in order to infer from it information and knowledge. Most of the data is discrete, which makes tables and graphs ideal candidates to store it, with tables having great advantages on both storing and querying, which are still the simplest and fastest. Especially in the computer era, where the amount of stored data is huge (think, for example, of the astronomical one) and there may be several thousands of people simultaneously updating it, but especially as crucial global and local decisions, be them in politics, intelligence, military, sci-ence, health, commerce, etc., are more and more heavily based on data, guaranteeing at least its plausibility is of paramount importance. Consequently, on one hand, more and more sophisticated data models were introduced, even if, commercially, from the implementation point of view, the vast majority of the existing database management systems are relational. This means that only part of the existing business rules may be enforced through them and for the rest we have to develop software appli-cations built on top of the corresponding Databases. On the other hand, just as starting to directly write Java (or C# or whatever other PL) code, immediately after getting some desired soft-ware application requirements, without proper problem analysis, software architecture and design is a huge mistake, starting to directly create tables in a database on a RDBMS is an even greater one: Databases are the foun-dations of db software applications. Just like no building resists earthquakes, tsunamis or even significant winds or rains if its foundations are not solid enough, no db software application may be easily designed, developed, maintained, and used if its underlying db was not properly designed and implemented.
eBook - PDFPrinciples of Database Management
The Practical Guide to Storing, Managing and Analyzing Big and Small Data
- Wilfried Lemahieu, Seppe vanden Broucke, Bart Baesens(Authors)
- 2018(Publication Date)
- Cambridge University Press(Publisher)
specialized types of data or structures. Two of these, XML and object-oriented Databases, were discussed earlier. Other types include: • Database systems to deal with time series and streaming events, such as Event Store and Axibase. Such systems represent data as a series of immut- able events over time, making it easier to support use cases such as event monitoring, complex event processing, or real-time analytics. Typically, availability and performance are of high concern for such systems. • Database systems to store and query geospatial data, supporting geospatial operators following the DE-9IM model, which defines relations between polygons as them being equal, touching, disjoint, contained, covered, or intersecting. For example, you can express a “within radius” query as follows: SELECT name, type, location, ST_Distance_Sphere(Point(-70, 40), location) AS distance_in_meters FROM restaurants WHERE type = "french cuisine" ORDER BY distance_in_meters LIMIT 10 • Database systems such as BayesDB, which lets users query the probable implication of their data (for example, to derive which fields in a table are the main predictors to estimate a certain outcome) and simulate what-if scenarios using a Bayesian query language, such as: SIMULATE gdp -- simulate gross domestic product FROM countries -- using table with information on countries -- given the following: GIVEN population_million = 1000, continent = 'asia' LIMIT 10; -- run 10 simulations Summary This chapter has discussed NoSQL Databases, a group of database management systems that have become quite popular throughout the past decade, and represents a shift in thinking toward schema-less structures, horizontal scalability, and non-relational data models and querying facilities. We note, however, that the explosion of popularity of NoSQL data storage layers should be put into perspective, considering their limitations.
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