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32-515: The terms data dictionary and data repository indicate a more general software utility than a catalogue. A catalogue is closely coupled with the DBMS software. It provides the information stored in it to the user and the DBA, but it is mainly accessed by the various software modules of the DBMS itself, such as DDL and DML compilers, the query optimiser, the transaction processor, report generators, and

64-722: A database transaction and thus they may be rolled back . A commonly used CREATE command is the CREATE TABLE command. The typical usage is: The column definitions are: An example statement to create a table named employees with a few columns is: Some forms of CREATE TABLE DDL may incorporate DML ( data manipulation language )-like constructs, such as the CREATE TABLE AS SELECT (CTaS) syntax of SQL. The DROP statement destroys an existing database, table, index, or view. A DROP statement in SQL removes

96-451: A collection of imperative verbs whose effect is to modify the schema of the database by adding, changing, or deleting definitions of tables or other elements. These statements can be freely mixed with other SQL statements, making the DDL not a separate language. The create command is used to establish a new database, table, index, or stored procedure . The CREATE statement in SQL creates

128-413: A component from a relational database management system (RDBMS). The types of objects that can be dropped depends on which RDBMS is being used, but most support the dropping of tables , users , and databases . Some systems (such as PostgreSQL ) allow DROP and other DDL commands to occur inside of a transaction and thus be rolled back . The typical usage is simply: For example, the command to drop

160-513: A component in a relational database management system (RDBMS). In the SQL 1992 specification, the types of components that can be created are schemas, tables , views , domains, character sets , collations , translations, and assertions. Many implementations extend the syntax to allow creation of additional elements, such as indexes and user profiles. Some systems, such as PostgreSQL and SQL Server , allow CREATE , and other DDL commands, inside

192-470: A data dictionary system is used only by the designers, users, and administrators and not by the DBMS Software, it is called a passive data dictionary. Otherwise, it is called an active data dictionary or data dictionary. When a passive data dictionary is updated, it is done so manually and independently from any changes to a DBMS (database) structure. With an active data dictionary, the dictionary

224-402: A range may be imposed on the value of numeric data in a data element (field), or a record in a table may be forced to participate in a set relationship with another record-type. Additionally, a distributed DBMS may have certain location specifics described within its active data dictionary (e.g. where tables are physically located). The data dictionary consists of record types (tables) created in

256-473: A schema manipulation language and schema information tables to query schemas. These information tables were specified as SQL/Schemata in SQL:2003 . The term DDL is also used in a generic sense to refer to any formal language for describing data or information structures. Many data description languages use a declarative syntax to define columns and data types. Structured Query Language (SQL), however, uses

288-430: A specific area. Other more recent electronics in the 2000s also have menus, such as digital media players . Menus are sometimes hierarchically organized, allowing navigation through different levels of the menu structure. Selecting a menu entry with an arrow will expand it, showing a second menu (the submenu) with options related to the selected entry. Usability of submenus has been criticized as difficult, because of

320-528: A table named employees is: The DROP statement is distinct from the DELETE and TRUNCATE statements, in that DELETE and TRUNCATE do not remove the table itself. For example, a DELETE statement might delete some (or all) data from a table while leaving the table itself in the database, whereas a DROP statement removes the entire table from the database. The ALTER statement modifies an existing database object. An ALTER statement in SQL changes

352-450: A voice-activated system, such as interactive voice response , a microphone sends a recording of the user's voice to a speech recognition system, which translates it to a command. A computer using a command line interface may present a list of relevant commands with assigned short-cuts (digits, numbers or characters) on the screen. Entering the appropriate short-cut selects a menu item. A more sophisticated solution offers navigation using

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384-411: Is a syntax for creating and modifying database objects such as tables, indices, and users. DDL statements are similar to a computer programming language for defining data structures , especially database schemas . Common examples of DDL statements include CREATE , ALTER , and DROP . If you see a .ddl file, that means the file contains a statement to create a table. Oracle SQL Developer contains

416-475: Is created when the Oracle Database is created. Developers may also use DDS context from free and open-source software (FOSS) for structured and transactional queries in open environments. Here is a non-exhaustive list of typical items found in a data dictionary for columns or fields: Data definition language In the context of SQL , data definition or data description language ( DDL )

448-407: Is no universal standard as to the level of detail in such a document. In the construction of database applications, it can be useful to introduce an additional layer of data dictionary software, i.e. middleware , which communicates with the underlying DBMS data dictionary. Such a "high-level" data dictionary may offer additional features and a degree of flexibility that goes beyond the limitations of

480-477: Is selecting the instruction that the symbol represents. A context menu is a menu in which the choices presented to the operator are automatically modified according to the current context in which the operator is working. A common use of menus is to provide convenient access to various operations such as saving or opening a file , quitting a program , or manipulating data. Most widget toolkits provide some form of pull-down or pop-up menu . Pull-down menus are

512-776: Is sometimes unclear, and so as to allow for multiple word menu names, the idea of a vertical menu was invented, as seen in NeXTSTEP . Menus are now also seen in consumer electronics , starting with TV sets and VCRs that gained on-screen displays in the early 1990s, and extending into computer monitors and DVD players . Menus allow the control of settings like tint , brightness , contrast , bass and treble , and other functions such as channel memory and closed captioning . Other electronics with text-only displays can also have menus, anything from business telephone systems with digital telephones, to weather radios that can be set to respond only to specific weather warnings in

544-466: Is supported by software companies which provide API services to MLS organizations. Developers use a data description specification (DDS) to describe data attributes in file descriptions that are external to the application program that processes the data, in the context of an IBM i . The sys.ts$ table in Oracle stores information about every table in the database. It is part of the data dictionary that

576-564: Is to create standardized rules to maintain data integrity and enforce business rules throughout one or more related applications. Some industries use generalized data dictionaries as technical standards to ensure interoperability between systems. The real estate industry, for example, abides by a RESO's Data Dictionary to which the National Association of REALTORS mandates its MLSs comply with through its policy handbook. This intermediate mapping layer for MLSs' native databases

608-421: Is updated first and changes occur in the DBMS automatically as a result. Database users and application developers can benefit from an authoritative data dictionary document that catalogs the organization, contents, and conventions of one or more databases. This typically includes the names and descriptions of various tables ( records or entities ) and their contents ( fields ) plus additional details, like

640-461: Is used to define referential integrity relationships, usually implemented as primary key and foreign key tags in some columns of the tables. These two statements can be included in a CREATE TABLE or an ALTER TABLE sentence; Menu (computing) In user interface design , a menu is a list of options presented to the user . A user chooses an option from a menu by using an input device . Some input methods require linear navigation:

672-471: The ASP.NET environment, Base One's data dictionary provides cross-DBMS facilities for automated database creation, data validation, performance enhancement ( caching and index utilization), application security , and extended data types . Visual DataFlex features provides the ability to use DataDictionaries as class files to form middle layer between the user interface and the underlying database. The intent

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704-408: The type and length of each data element . Another important piece of information that a data dictionary can provide is the relationship between tables. This is sometimes referred to in entity-relationship diagrams (ERDs), or if using set descriptors, identifying which sets database tables participate in. In an active data dictionary constraints may be placed upon the underlying data. For instance,

736-581: The ability to export from an ERD generated with Data Modeler to either a .sql file or a .ddl file. The concept of the data definition language and its name was first introduced in relation to the Codasyl database model, where the schema of the database was written in a language syntax describing the records , fields , and sets of the user data model . Later it was used to refer to a subset of Structured Query Language (SQL) for declaring tables , columns, data types and constraints . SQL-92 introduced

768-569: The amount of programming required to build menus , forms , reports, and other components of a database application, including the database itself. For example, PHPLens includes a PHP class library to automate the creation of tables, indexes, and foreign key constraints portably for multiple databases. Another PHP-based data dictionary, part of the RADICORE toolkit, automatically generates program objects , scripts , and SQL code for menus and forms with data validation and complex joins . For

800-587: The constraint enforcer. On the other hand, a data dictionary is a data structure that stores metadata , i.e., (structured) data about information. The software package for a stand-alone data dictionary or data repository may interact with the software modules of the DBMS, but it is mainly used by the designers, users and administrators of a computer system for information resource management. These systems maintain information on system hardware and software configuration, documentation, application and users as well as other information relevant to system administration. If

832-456: The cursor keys or the mouse (even in two dimensions; then the menu items appear or disappear similarly to the menus common in GUIs). The current selection is highlighted and can be activated by pressing the enter key. A computer using a graphical user interface presents menus with a combination of text and symbols to represent choices. By clicking on one of the symbols or text, the operator

864-485: The database by systems generated command files, tailored for each supported back-end DBMS. Oracle has a list of specific views for the "sys" user. This allows users to look up the exact information that is needed. Command files contain SQL Statements for CREATE TABLE , CREATE UNIQUE INDEX , ALTER TABLE (for referential integrity), etc., using the specific statement required by that type of database. There

896-459: The narrow height that must be crossed by the pointer . The steering law predicts that this movement will be slow, and any error in touching the boundaries of the parent menu entry will hide the submenu. Some techniques proposed to alleviate these errors are keeping the submenu open while moving the pointer in diagonal, and using mega menus designed to enhance scannability and categorization of its contents. Negative user experience with submenus

928-709: The native "low-level" data dictionary, whose primary purpose is to support the basic functions of the DBMS, not the requirements of a typical application. For example, a high-level data dictionary can provide alternative entity-relationship models tailored to suit different applications that share a common database. Extensions to the data dictionary also can assist in query optimization against distributed databases . Additionally, DBA functions are often automated using restructuring tools that are tightly coupled to an active data dictionary. Software frameworks aimed at rapid application development sometimes include high-level data dictionary facilities, which can substantially reduce

960-441: The properties of an object inside of a relational database management system (RDBMS). The types of objects that can be altered depends on which RDBMS is being used. The typical usage is: For example, the command to add (then remove) a column named bubbles for an existing table named sink is: The TRUNCATE statement is used to delete all data from a table. It's much faster than DELETE . Another type of DDL sentence in SQL

992-497: The type commonly used in menu bars (usually near the top of a window or screen), which are most often used for performing actions, whereas pop-up (or "fly-out") menus are more likely to be used for setting a value, and might appear anywhere in a window. According to traditional human interface guidelines, menu names were always supposed to be verbs , such as "file", "edit" and so on. This has been largely ignored in subsequent user interface developments. A single-word verb however

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1024-449: The user must move a cursor or otherwise pass from one menu item to another until reaching the selection. On a computer terminal , a reverse video bar may serve as the cursor. Touch user interfaces and menus that accept codes to select menu options without navigation are two examples of non-linear interfaces. Some of the input devices used in menu interfaces are touchscreens , keyboards , mice , remote controls , and microphones. In

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