The SQL Standard says that all SQL operations are executed within an SQL-environment. An SQL-environment has six components.

  1. One SQL-agent responsible for causing the execution of SQL statements. It is usually an application program that calls one or more externally-invoked procedures in an SQL-client Module.
  2. One SQL-implementation; a database management system (DBMS) that executes SQL statements. Your SQL-agent considers your DBMS to have two components: (a) one SQL-client, to which the SQL-agent is bound, and (b) one or more SQL-servers to manage your SQL-data. (SQL-data consists of the descriptions of all the SQL Objects, plus all the data values you can access with your DBMS.) The SQL-client is the part of your DBMS that establishes connections to the SQL-servers; it maintains a diagnostics area and other state data that relate to the interactions between the DBMS and the SQL-agent. Each SQL- server has three responsibilities: (a) it manages the SQL-session taking place over the SQL-Connection between itself and the SQL-client, (b) it executes SQL statements received from the SQL-client, receiving and sending data as required, and (c) it maintains the state of the SQL-session, including the <AuthorizationID> and certain session defaults. The method of communication between the SQL-client and the SQL-server(s) is implementation-defined, but the Standard does specify how an SQL- agent will communicate with your DBMS (see SQL Binding Styles).
  3. Zero or more SQL-client Modules, each containing zero or more externally-invoked procedures. SQL-client Modules are programming modules -- exactly one is associated with an SQL-agent at any time.
  4. Zero or more <AuthorizationID>s. An SQL <AuthorizationID>, or authorization identifier, represents a user of SQL-data.
  5. Zero or more Catalogs.
  6. Zero or more sites (e.g., Base tables) that contain SQL-data.

In short, an SQL-environment can be thought of as a specific operation of a DBMS on the collection of Catalogs (that contain SQL-data) within a specified SQL-server by all the users (that is, all persons and programs) that have authority to access the SQL-server during the time the DBMS is operating.

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Portions of the text in this entry are Copyright © 1999 by Ocelot Computer Services Incorporated. Used by permission.

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