Bonus Content. Glossary

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1 Bonus Content Glossary ActiveX control: A reusable software component that can be added to an application, reducing development time in the process. ActiveX is a Microsoft technology; ActiveX components can be used only by developers who work on Windows development systems. aggregate function: A function that produces a single result based on the contents of an entire set of table rows. Also called a set function. alias: A short substitute or nickname for a table name. applet: A small application, written in the Java language, stored on a Web server that is downloaded to and executed on a Web client that connects to the server. application program interface (API): A standard means of communicating between an application and a database or other system resource. assertion: A constraint that is specified by a CREATE ASSERTION statement (rather than by a clause of a CREATE TABLE statement). Assertions commonly apply to more than one table. atomic: Incapable of being subdivided. attribute: A component of a structured type or relation. back end: That part of a DBMS that interacts directly with the database. catalog: A named collection of schemas. client: An individual user workstation that represents the front end of a DBMS the part that displays information on a screen and responds to user input. client/server system: A multiuser system in which a central processor (the server) is connected to multiple intelligent user workstations (the clients). cluster: A named collection of catalogs. CODASYL DBTG database model: The network database model. Note: This use of the term network refers to the structuring of the data (network as opposed to hierarchy), rather than to network communications.

2 BC2 SQL For Dummies, 7th Edition collating sequence: The ordering of characters in a character set. All collating sequences for character sets that have the Latin characters (a, b, c) define the obvious ordering (a, b, c,...). They differ, however, in the ordering of special characters (+,, <,?, and so on) and in the relative ordering of the digits and the letters. collection type: A data type that allows a field of a table row to contain multiple objects. column: A table component that holds a single attribute of the table. composite key: A key made up of two or more table columns. conceptual view: The schema of a database. concurrent access: Two or more users operating on the same rows in a database table at the same time. constraint: A restriction you specify on the data in a database. constraint, deferred: A constraint that is not applied until you change its status to immediate or until you COMMIT the encapsulating transaction. cursor: An SQL feature that specifies a set of rows, an ordering of those rows, and a current row within that ordering. Data Control Language (DCL): That part of SQL that protects the database from harm. Data Definition Language (DDL): That part of SQL used to define, modify, and eradicate database structures. Data Manipulation Language (DML): That part of SQL that operates on database data. data redundancy: Having the same data stored in more than one place in a database. data source: A source of data used by a database application. It may be a database or a flat data file. data sublanguage: A subset of a complete computer language that deals specifically with data handling. SQL is a data sublanguage. data type: A set of representable values. database: A self-describing collection of integrated records.

3 Glossary BC3 database, enterprise: A database containing information used by an entire enterprise. database, personal: A database designed for use by one person on a single computer. database, workgroup: A database designed to be used by a department or workgroup within an organization. database administrator (DBA): The person ultimately responsible for the functionality, integrity, and safety of a database. database engine: That part of a DBMS that directly interacts with the database (serving as part of the back end). database publishing: The act of making the database contents available on the Internet or over an intranet. database server: The server component of a client/server system. DB2: A relational database management system marketed by IBM Corporation. DBMS: A database management system. deletion anomaly: An inconsistency in a multitable database that occurs when a row is deleted from one of its tables. descriptor: An area in memory used to pass information between an application s procedural code and its dynamic SQL code. diagnostics area: A data structure, managed by the DBMS, that contains detailed information about the last SQL statement executed and any errors that occurred during its execution. distributed data processing: A system in which multiple servers handle data processing. domain: The set of all values that a database item can assume. domain integrity: A property of a database table column where all data items in that column fall within the domain of the column. driver: That part of a database management system that interfaces directly with a database. Drivers are part of the back end. driver manager: A component of an ODBC-compliant database interface. On Windows machines, the driver manager is a dynamic link library (DLL) that coordinates the linking of data sources with appropriate drivers.

4 BC4 SQL For Dummies, 7th Edition entity integrity: A property of a database table that is entirely consistent with the real-world object that it models. file server: The server component of a resource-sharing system. It does not contain any database management software. firewall: A piece of software (or a combination of hardware and software) that isolates an intranet from the Internet, allowing only trusted traffic to travel between them. flat file: A collection of data records having minimal structure. foreign key: A column or combination of columns in a database table that references the primary key of another table in the database. forest: A collection of elements in an XML document. front end: That part of a DBMS (such as the client in a client/server system) that interacts directly with the user. functional dependency: A relationship between or among attributes of a relation. hierarchical database model: A tree-structured model of data. host variable: A variable passed between an application written in a procedural host language and embedded SQL. HTML (HyperText Markup Language): A standard formatting language for Web documents. implementation: A particular relational DBMS running on a specific hardware platform. index: A table of pointers used to locate rows rapidly in a data table. information schema: The system tables, which hold the database s metadata. insertion anomaly: An inconsistency introduced into a multitable database when a new row is inserted into one of its tables. Internet: The worldwide network of computers. intranet: A communication network used within a single organization. IPX/SPX: A local area network protocol. Java: A platform-independent, compiled language used in many open-source applications.

5 Glossary BC5 JavaScript: A script language that gives some measure of programmability to HTML-based Web pages. JDBC (Java DataBase Connectivity): A standard interface between a Java applet or application and a database. The JDBC standard is modeled after the ODBC standard. join: A relational operator that combines data from multiple tables into a single result table. logical connectives: Used to connect or change the truth value of predicates to produce more complex predicates. mapping: The translation of data in one format to another format. metadata: Data about the structure of the data in a database. modification anomaly: A problem introduced into a database when a modification (insertion, deletion, or update) is made to one of the database tables. module language: A form of SQL in which SQL statements are placed in modules, which are called by an application program written in a host language. mutator function: A function associated with a user-defined type (UDT), having two parameters whose definition is implied by the definition of some attribute of the type. The first parameter (the result) is of the same type as the UDT. The second parameter has the same type as the defining attribute. MySQL: The most popular open-source relational database management system in the world. nested query: A statement that contains one or more subqueries. NetBEUI: A local area network protocol. network database model: A way of organizing a database to get minimum redundancy of data items by allowing any data item (node) to be directly connected to any other. normalization: A technique that reduces or eliminates the possibility that a database is subject to modification anomalies. object: Any uniquely identifiable thing. ODBC (Open DataBase Connectivity): A standard interface between a database and an application that is trying to access the data in that database. ODBC is defined by an international (ISO) and a national (ANSI) standard.

6 BC6 SQL For Dummies, 7th Edition Oracle: A relational database management system marketed by Oracle Corporation. parameter: A variable within an application written in SQL module language. PostgreSQL: A powerful open-source relational database management system. precision: The maximum number of digits allowed in a numeric data item. predicate: A statement that may be either logically true or logically false. primary key: A column or combination of columns in a database table that uniquely identifies each row in the table. procedural language: A computer language that solves a problem by executing a procedure in the form of a sequence of steps. query: A question you ask about the data in a database. rapid application development (RAD) tool: A proprietary, graphically oriented alternative to SQL. A number of such tools are on the market. record: A representation of some physical or conceptual object. reference type: A data type whose values are all potential references to sites of one specified data type. referential integrity: A state in which all the tables in a database are consistent with each other. relation: A two-dimensional array of rows and columns, containing singlevalued entries and no duplicate rows. reserved words: Words that have a special significance in SQL and cannot be used as variable names or in any other way that differs from their intended use. row: A sequence of (field name, value) pairs. row value expression: A list of value expressions enclosed in parentheses and separated by commas. scale: The number of digits in the fractional part of a numeric data item. schema: The structure of an entire database. The information that describes the schema is the database s metadata.

7 Glossary BC7 schema owner: The person who was designated as the owner when the schema was created. SEQUEL: A data sublanguage created by IBM that was a precursor of SQL. set function: A function that produces a single result based on the contents of an entire set of table rows. Also called an aggregate function. SQL: An industry standard data sublanguage, specifically designed to create, manipulate, and control relational databases. SQL, dynamic: A means of building compiled applications that does not require all data items to be identifiable at compile time. SQL, embedded: An application structure in which SQL statements are embedded within programs written in a host language. SQL, interactive: A real-time conversation with a database. SQL/DS: A relational database management system marketed by IBM Corporation. SQL Server: A relational database management system developed and marketed by Microsoft Corporation. structured type: A user-defined type that is expressed as a list of attribute definitions and methods rather than being based on a single predefined source type. subquery: A query within a query. subtype: A data type is a subtype of a second data type if every value of the first type is also a value of the second type. supertype: A data type is a supertype of a second data type if every value of the second type is also a value of the first type. table: A relation. TCP/IP (Transmission Control Protocol/Internet Protocol): The network protocol used by the Internet and intranets. teleprocessing system: A powerful central processor connected to multiple dumb terminals. transaction: A sequence of SQL statements whose effect is not accessible to other transactions until all the statements are executed.

8 BC8 SQL For Dummies, 7th Edition transitive dependency: One attribute of a relation depends on a second attribute, which in turn depends on a third attribute. translation table: Tool for converting character strings from one character set to another. trigger: A small piece of code that tells a DBMS what other actions to perform after certain SQL statements have been executed. update anomaly: A problem introduced into a database when a table row is updated. user-defined type (UDT): A type whose characteristics are defined by a type descriptor specified by the user. value expression: An expression that combines two or more values. value expression, conditional: A value expression that assigns different values to arguments, based on whether a condition is logically true. value expression, datetime: A value expression that deals with DATE, TIME, TIMESTAMP, or INTERVAL data. value expression, numeric: A value expression that combines numeric values using the addition, subtraction, multiplication, or division operator. value expression, string: A value expression that combines character strings with the concatenation operator. value function: A function that performs an operation on a single character string, number, or date/time. view: A database component that behaves exactly like a table but has no independent existence of its own. virtual table: A view. World Wide Web: An aspect of the Internet that has a graphical user interface. The Web is accessed by applications called Web browsers, and information is provided to the Web by installations called Web servers. XML: A widely accepted markup language used as a means of exchanging data between dissimilar systems.

Index COPYRIGHTED MATERIAL. Symbols and Numerics

Index COPYRIGHTED MATERIAL. Symbols and Numerics Symbols and Numerics % (percent sign) wildcard, 218 220 * (asterisk), 140, 245, 334 _ (underscore) wildcard, 218 220 (concatenation operator), 65 66, 178 = (equal operator), 274 1NF (first normal form),