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In database packages, the term cursor refers to a control structure for the successive traversal (and potential processing) of records in a result set as returned by a query. The term database originated within the computer industry, though its meaning has been broadened by popular use,includes non-electronic databases within its definition. ...
In computer science, a database record is a description of a single item as stored in a database. ...
An SQL result set is a set of rows from a database, as well as meta-information about the query such as number of results returned and the column names. ...
Cursors may be implemented on the client side or the server side of the database connection. A client-side cursor is necessary for processing individual rows returned from the database because many languages do not offer any other mechanism for manipulating individual rows in the result set. In this way, a cursor can be thought of as an iterator over the collection of rows in the result set. In computer science, an iterator is an object allowing one to sequence through all of the elements or parts contained in some other object, typically a container or list. ...
Several database operations do not provide an opportunity for the use of cursors. The INSERT statement, for example, as well as most forms of the DELETE and UPDATE statements. Even a SELECT statement may not involve the use of a cursor if it returns no rows, or only one row. An SQL INSERT statement adds one or more records to a table in a relational database. ...
A DELETE statement in SQL removes records in a relational database management system. ...
An UPDATE statement in SQL changes data in one or more records in a relational database management system. ...
On the server side, a cursor similarly allows an SQL statement's results to be used or examined one row at a time. Typically, server-side cursors are not necessary because most statements can be written using other SQL constructs that allow the database to carry out the intended operations more efficiently. They are rarely required.
Types of cursors: Static, Dynamic, Forward-only, Keyset-driven.
Disadvantages of cursors: Each time you fetch a row from the cursor, it results in a network round trip, where as a normal SELECT query makes only one round trip, however large the result set is. Cursors are also costly because they require more resources and temporary storage (results in more I/O operations). Further, there are restrictions on the SELECT statements that can be used with some types of cursors. In telecommunications, the term round-trip delay time or round-trip time (RTT) has the following meanings: The elapsed time for transit of a signal over a closed circuit, or time elapsed for a message to a remote place and back again. ...
An SQL result set is a set of rows from a database, as well as meta-information about the query such as number of results returned and the column names. ...
In computing, Input/output, or I/O, is the collection of interfaces that different functional units (sub-systems) of an information processing system use to communicate with each other, or the signals (information) sent through those interfaces. ...
A SELECT statement in SQL returns a result set of records from one or more tables. ...
References
- Christopher J. Date: Database in Depth, O'Reilly & Associates, ISBN 0-596-10012-4
- Thomas M. Connolly, Carolyn E. Begg: Database Systems, Addison-Wesley, ISBN 0-321-21025-5
- Ramiz Elmasri, Shamkant B. Navathe: Fundamentals of Database Systems, Addison-Wesley, ISBN 0-201-54263-3
- Neil Matthew, Richard Stones: Beginning Databases with PostgreSQL: From Novice to Professional, Apress, ISBN 1-59059-478-9
- Thomas Kyte: Expert One-On-One: Oracle, Apress, ISBN 1-59059-525-4
Christopher J. Date is an independent author, lecturer, researcher, and consultant, specializing in relational database technology. ...
His portrait Thomas Kyte is a Vice President in Oracle Corporation. ...
See also In computer science, an iterator is an object allowing one to sequence through all of the elements or parts contained in some other object, typically a container or list. ...
External links | Topics in database management systems (DBMS) ( view • talk • edit ) | | Concepts
Database | Database model | Relational database | Relational model | Relational algebra | Primary key - Foreign key - Surrogate key - Superkey
Database normalization | Referential integrity | Relational DBMS | Distributed DBMS | ACID To meet Wikipedias quality standards, this article or section may require cleanup. ...
The term database originated within the computer industry, though its meaning has been broadened by popular use,includes non-electronic databases within its definition. ...
A database model is a theory or specification describing how a database is structured and used. ...
A relational database is a database that conforms to the relational model. ...
The relational model for database management is a database model based on predicate logic and set theory. ...
Relational algebra, an offshoot of first-order logic, is a set of relations closed under operators. ...
In database design, a primary key is a value that can be used to identify a unique row in a table. ...
A foreign key (FK) is a field or group of fields in a database record that point to a key field or group of fields forming a key of another database record in some (usually different) table. ...
Dr. E. F. Codd, the creator of the Relational Model defined a surrogate key as ..Database users may cause the system to generate or delete a surrogate, but they have no control over its value, nor is its value ever displayed to them . ...
A superkey is defined in the relational model as a set of attributes of a relation for which it holds that in all instances of the relation there are no two distinct tuples that have the same values for the attributes in this set. ...
This article or section is in need of attention from an expert on the subject. ...
An example of a database that has not enforced referential integrity. ...
A relational database management system (RDBMS) is a database management system (DBMS) that is based on the relational model as introduced by Edgar F. Codd. ...
According to Elmasri and Navathe (2004, p. ...
For other uses, see Acid (disambiguation). ...
| Objects
Trigger | View | Table | Cursor | Log | Transaction | Index | Stored procedure | Partition A database trigger is procedural code that is automatically executed in response to certain events on a particular table in a database. ...
Originally, in database theory, a view is a read only virtual or logical table composed of the result set of a query. ...
In relational databases and SQL databases a table is a set of data elements (values) that is organized using a model of horizontal rows and vertical columns. ...
In in the field of databases in computer science, a transaction log (also database log or binary log) is a history of actions executed by a database management system to guarantee ACID properties over crashes or hardware failures. ...
A database transaction is a unit of interaction with a database management system or similar system that is treated in a coherent and reliable way independent of other transactions that must be either entirely completed or aborted. ...
An index is a feature in a database that allows quick access to the rows in a table. ...
A stored procedure is a subroutine available to applications accessing a relational database system. ...
A partition is a division of a logical database or its constituting elements into distinct independent parts. ...
| Topics in SQL
Select | Insert | Update | Merge | Delete | Join | Union | Create | Drop
Comparison of syntax SQL (commonly expanded to Structured Query Language — see History for the terms derivation) is the most popular computer language used to create, modify, retrieve and manipulate data from relational database management systems. ...
A SELECT statement in SQL returns a result set of records from one or more tables. ...
An SQL INSERT statement adds one or more records to a table in a relational database. ...
An UPDATE statement in SQL changes data in one or more records in a relational database management system. ...
Wikipedia does not have an article with this exact name. ...
A DELETE statement in SQL removes records in a relational database management system. ...
A join combines records from two or more tables in a relational database. ...
UNION Combines the results of two or more queries into a single result set consisting of all the rows belonging to all queries in the union. ...
A CREATE statement in SQL creates an object inside of a relational database management system (RDBMS). ...
A DROP statement in SQL removes an object from a relational database management system (RDBMS). ...
This article gives a brief summary of various SQL syntax differences used in popular SQL engines: DB2 Firebird / InterBase MySQL MSSQL Oracle PostgreSQL SQLite OpenLink Virtuoso // A method to somehow escape identifiers (table, column names, etc), so they do not have to obey regular identifier rules, such as not colliding...
| | | Implementations of database management systems | | Types of implementations
Flat file | Deductive | Dimensional | Hierarchical | Object oriented | Temporal
Products
db4o | dBASE | Oracle | Caché | OpenLink Virtuoso | Sybase | Ingres | MySQL | SQLite | Microsoft SQL Server | PostgreSQL | DB2 | Informix | Helix database | Teradata | Pyrrho DBMS | Comparison - relational | Comparison - object-relational A flat file database is described by a very simple database model, where all the information is stored in text files. ...
A deductive database system is a database system which can make deductions (ie: infer additional rules or facts) based on rules and facts stored in the (deductive) database. ...
A dimensional database is one which, rather than storing data in multiple two dimensional tables (as a relational databases does), represents key data entities as different dimensions. ...
To meet Wikipedias quality standards, this article or section may require cleanup. ...
In an object oriented database, information is represented in the form of objects like in object oriented programming. ...
A temporal database is a database management system with built-in time aspects, e. ...
There are very few or no other articles that link to this one. ...
dBASE III The correct title of this article is dBASE. The initial letter is capitalized because of technical restrictions. ...
An Oracle database consists of a collection of data managed by an Oracle database management system. ...
Caché is a proprietary M technology-based database management system from InterSystems. ...
The current version of the article or section reads like an advertisement. ...
Sybase SQL Server was the name of Sybase Corporations primary relational database management system product from 1987 to 1995. ...
Ingres (pronounced ingress) is a commercially supported, open-source relational database management system. ...
MySQL is a multithreaded, multi-user, SQL Database Management System (DBMS) with more than six million installations. ...
SQLite is an ACID-compliant relational database management system contained in a relatively small C library. ...
Microsoft SQL Server is a relational database management system (RDBMS) produced by Microsoft. ...
PostgreSQL is a free object-relational database server (database management system), released under a flexible BSD-style license. ...
DB2 is IBMs line of RDBMS (or, as IBM now calls it, data server) software products within IBMs broader Information Management software line. ...
Informix is a family of relational database management system products from IBM, acquired in 2001 from a company (also called Informix or Informix Software) which dates its origins back to 1980. ...
Helix is a pioneering database management system for the Apple Macintosh platform. ...
Teradata Teradata is a relational database management system initially created by the firm with the same name, founded in 1979. ...
It has been suggested that List of relational database management systems be merged into this article or section. ...
The following tables compare general and technical information for a number of object-relational database management systems. ...
| Components
Query language | Query optimizer | Query plan | ODBC | JDBC
Lists
List of object-oriented database management systems
List of relational database management systems
List of truly relational database management systems Query languages are computer languages used to make queries into databases and information systems. ...
The query optimizer is a component of database management system that is used to analyzes queries submitted to database server for execution, and then determines the optimal way to execute the query. ...
A query plan (or query execution plan) is an set of steps used to access information in a SQL relational database management system. ...
In computing, Open Database Connectivity (ODBC) provides a standard software API method for using database management systems (DBMS). ...
Java Database Connectivity, or JDBC, is an API for the Java programming language that defines how a client may access a database. ...
The following is a list of object-oriented database management systems. ...
It has been suggested that List of truly relational database management systems be merged into this article or section. ...
It has been suggested that this article or section be merged into List of relational database management systems. ...
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