Glosario de Bases de Datos Sybase, "R"

A query that requests data within a specific range of values. These include greater than and less than queries, queries using between, and some queries using like.

See relational database management system (RDBMS) .

Permission to read an object (for example, to select rows from a table). See also permissions .

See row .

The process of rebuilding one or more databases from database and log dump s. See also automatic recovery .

The rules governing data consistency, specifically the relationships among the primary keys and foreign keys of different tables. Adaptive Server addresses referential integrity with user-defined triggers and with referential integrity constraints .

A requirement that data inserted into a "referencing" table, the table that defines the constraint, must have matching values in a "referenced" table. You cannot delete rows or update column values from a referenced table that match values in a referencing table. Also, you cannot drop the referenced table until the referencing table is dropped or the referential integrity constraint is removed.

A strategy used by Adaptive Server to resolve join queries on large tables that have no useful index. Adaptive Server builds a temporary clustered index on the join columns of the inner table, and uses this index to retrieve the rows. Adaptive Server estimates the cost of this strategy and the cost of the alternative¾a table scan¾and chooses the least expensive method.

A set of related data tables and other database object s that are organized and presented to serve a specific purpose. See also data warehouse .

A system for storing and retrieving data from two-dimensional tables in which the use of SQL is standard.

A type of Boolean or logical expression of the form:
arith_expressionrelational_operator  arith_expression

In Transact-SQL, a relational expression can return TRUE, FALSE, or UNKNOWN. The results can evaluate to UNKNOWN if one or both of the expressions evaluates to NULL.

An operator that compares two operands and yields a truth value, such as "5 < 7" (TRUE), "ABC" = "ABCD" (FALSE) or "@value > NULL" (UNKNOWN).

A description of how entities are related. A basic step in logical design of a database is to identify the relationships between the entities you have identified. See also entity .

A login to a remote server.

A stored procedure that is executed on an Adaptive Server other than the server the user is logged into.

See correlated subquery .

For databases, a process by which the changes to data in one database (including creation, updating, and deletion of records) are also applied to the corresponding records in other database.

See keyword .

The time it takes for a single task, such as sending a Transact-SQL query to Adaptive Server, to complete. See also initial response time .

See selection .

A value that indicates that the procedure completed successfully or indicates the reason for failure.

See row ID .

Titles recognized by Adaptive Server that provide individual accountability for users performing system administration and security-related tasks in Adaptive Server. The System Administrator , System Security Officer , and Operator roles can be granted to individual server login accounts. In addition to these system roles, a System Security Officer can create user-defined roles, such as "financial analyst" and "salary administrator".

A Transact-SQL statement used with a user-defined transaction , before a committransaction has been received, that cancels the transaction and undoes any changes that were made to the database.

A set of related column s that describes a specific entity . Also called a record.

Functions (sum, avg, min, max, and count ) that generate a new row for summary data when used with compute in a select statement .

A unique, internal identifier for a data row . The row ID, or RID, is a combination of the data page number and the row number on the page.

See remote procedure call (RPC) .

A specification that controls what data can be entered in a particular column or in a column of a particular user-defined datatype .

The value of the configuration parameter currently in use.