Computer Science
Query Data
Query data refers to the process of requesting specific information from a database using a query language such as SQL. This allows users to retrieve, filter, and manipulate data based on their specific requirements. Query data is essential for extracting meaningful insights and generating reports from large datasets, making it a fundamental concept in database management and data analysis.
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3 Key excerpts on "Query Data"
eBook - ePub- Arthur C. Graesser, John B. Black, Arthur C. Graesser, John B. Black(Authors)
- 2017(Publication Date)
- Taylor & Francis(Publisher)
13 Data Base Querying by ComputerSteven P. Shwartz Cognitive Systems Inc .Wendy G. Lehnert Univ. of Massachusetts AmherstThe computer-human interface problem is rapidly becoming a critical concern to the data processing industry. Computerized data bases are currently available for a wide spectrum of applications ranging from marketing to law to finance. The computer systems attached to these data bases can, in principle, provide answers to an enormous number of user questions. But in fact, only a small percentage of the potential user population knows how to formulate queries to a data base, i.e., only those with data processing skills.Data Base Querying: A Brief History
Natural language processing technology represents an enormous advance in the user-friendliness of computer systems. In the following section, we present a brief history of the development of user-friendly systems in order to put this new technology in perspective.Programming Languages
The earliest computer data base query systems required queries written in machine or assembler language. To program in machine or assembler language one needs a knowledge of the physical structure of the data base, a knowledge of programming constructs such as loops, variables, and procedures, and a knowledge of the architecture of the machine on which the data base resides. Such programming skills are present in only a very small percentage of the potential user population for most data bases.The development of high-level languages, such as FORTRAN, reduced the requisite level of programming expertise. A program written in a particular high-level language will run with virtually no modification on a wide variety of different computers. For this reason, high-level programmers do not need to be knowledgeable concerning computer architecture. However, considerable programming skill is still necessary to access a data base using even high-level languages. A high-level programmer must still know about the physical structure of the data base and have an understanding of programming concepts.
eBook - PDF- Mark L. Gillenson(Author)
- 2012(Publication Date)
- Wiley(Publisher)
Data definition, which is operationalized with a data definition language (DDL), involves instructing the DBMS software on what tables will be in the database, what attributes will be in the tables, which attributes will be indexed, and so forth. Data manipulation refers to the four basic operations that can and must be performed on data stored in any DBMS (or in any other data storage arrangement, for that matter): data retrieval, data update, insertion of new records, and deletion of existing records. Data manipulation requires a special language with which users can communicate data manipulation commands to the DBMS. Indeed, as a class, these are known as data manipulation languages (DMLs). A standard language for data management in relational databases, known as Structured Query Language or SQL, was developed in the early 1980s. SQL incorporates both DDL and DML features. It was derived from an early IBM research project in relational databases called ‘‘System R.’’ SQL has long since been declared a standard by the American National Standards Institute (ANSI) and by the International Standards Organization (ISO). Indeed, several versions of the standards have been issued over the years. Using the standards, many manufacturers have produced versions of SQL that are all quite similar, at least at the level at which we will look at SQL in this book. These SQL versions are found in such mainstream DBMSs as DB2, Oracle, MS Access, Informix, and others. SQL in its various imple- mentations is used very heavily in practice today by companies and organizations of every description, Advance Auto Parts being one of countless examples. SQL is a comprehensive database management language. The most interesting aspect of SQL and the aspect that we want to explore in this chapter is its rich data retrieval capability.
eBook - PDF- Paul Murrell(Author)
- 2009(Publication Date)
- Chapman and Hall/CRC(Publisher)
SQL > SELECT dt.date date, lt.longitude long, lt.latitude lat, ozone FROM measure_table mt INNER JOIN date_table dt ON mt.date = dt.ID INNER JOIN location_table lt ON mt.location = lt.ID WHERE mt.location = 1; date long lat ozone ----------------------------1995-01-16 -113.75 36.25 304.0 1995-02-16 -113.75 36.25 296.0 1995-03-16 -113.75 36.25 312.0 1995-04-16 -113.75 36.25 326.0 ... 158 Introduction to Data Technologies In this chapter we will gain these two useful skills: how to use SQL to per-form necessary tasks with a database—the sorts of things that are quite straightforward with other storage formats— and how to use SQL to per-form tasks with a database that are much more sophisticated than what is possible with other storage options. 7.2 Querying databases SQL is a language for creating, configuring, and querying relational databases. It is an open standard that is implemented by all major DBMS software, which means that it provides a consistent way to communicate with a database no matter which DBMS software is used to store or access the data. Like all languages, there are different versions of SQL. The information in this chapter is consistent with SQL-92. SQL consists of three components: Data Definition Language (DDL) This is concerned with the creation of databases and the specification of the structure of tables and of constraints between tables. This part of the language is used to specify the data types of each column in each table, which column(s) make up the primary key for each table, and how foreign keys are related to primary keys. We will not discuss this part of the language in this chapter, but some mention of it is made in Section 8.3. Data Control Language (DCL) This is concerned with controlling access to the database— who is allowed to do what to which tables. This part of the language is the domain of database administrators and need not concern us.
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