Result set

Last updated

A result set is the set of results returned by a query, usually in the same format as the database the query is called on. [1] For example, in SQL, which is used in conjunction with relational databases, it is the result of a SELECT query on a table or view and is itself a non-permanent table of rows, and could include metadata about the query such as the column names, and the types and sizes of each column. In an object database, the result set is usually a collection of objects from the database.

Depending on the database, the number of rows in the result set may or may not be known. Usually, this number is not known up front because the result set is built on the fly. A cursor can be used by client applications to fetch a few rows of the result set at a time. [2]

Sorting

There is no guarantee that the rows of a result set returned by a SELECT query are in any particular order unless the ORDER BY clause is used in the query, which sorts the rows of the result set in ascending or descending order based on one or more columns. [2]

Related Research Articles

A relational database is a database based on the relational model of data, as proposed by E. F. Codd in 1970. A database management system used to maintain relational databases is a relational database management system (RDBMS). Many relational database systems are equipped with the option of using SQL for querying and updating the database.

The relational model (RM) is an approach to managing data using a structure and language consistent with first-order predicate logic, first described in 1969 by English computer scientist Edgar F. Codd, where all data is represented in terms of tuples, grouped into relations. A database organized in terms of the relational model is a relational database.

<span class="mw-page-title-main">Join (SQL)</span> SQL clause

A join clause in the Structured Query Language (SQL) combines columns from one or more tables into a new table. The operation corresponds to a join operation in relational algebra. Informally, a join stitches two tables and puts on the same row records with matching fields : INNER, LEFT OUTER, RIGHT OUTER, FULL OUTER and CROSS.

The SQL SELECT statement returns a result set of records, from one or more tables.

An SQL INSERT statement adds one or more records to any single table in a relational database.

A table is a collection of related data held in a table format within a database. It consists of columns and rows.

A query plan is a sequence of steps used to access data in a SQL relational database management system. This is a specific case of the relational model concept of access plans.

A database index is a data structure that improves the speed of data retrieval operations on a database table at the cost of additional writes and storage space to maintain the index data structure. Indexes are used to quickly locate data without having to search every row in a database table every time said table is accessed. Indexes can be created using one or more columns of a database table, providing the basis for both rapid random lookups and efficient access of ordered records.

A user-defined function (UDF) is a function provided by the user of a program or environment, in a context where the usual assumption is that functions are built into the program or environment. UDFs are usually written for the requirement of its creator.

<span class="mw-page-title-main">Null (SQL)</span> Marker used in SQL databases to indicate a value does not exist

In SQL, null or NULL is a special marker used to indicate that a data value does not exist in the database. Introduced by the creator of the relational database model, E. F. Codd, SQL null serves to fulfil the requirement that all true relational database management systems (RDBMS) support a representation of "missing information and inapplicable information". Codd also introduced the use of the lowercase Greek omega (ω) symbol to represent null in database theory. In SQL, NULL is a reserved word used to identify this marker.

SPARQL is an RDF query language—that is, a semantic query language for databases—able to retrieve and manipulate data stored in Resource Description Framework (RDF) format. It was made a standard by the RDF Data Access Working Group (DAWG) of the World Wide Web Consortium, and is recognized as one of the key technologies of the semantic web. On 15 January 2008, SPARQL 1.0 was acknowledged by W3C as an official recommendation, and SPARQL 1.1 in March, 2013.

Set operations in SQL is a type of operations which allow the results of multiple queries to be combined into a single result set.

<span class="mw-page-title-main">Database model</span> Type of data model

A database model is a type of data model that determines the logical structure of a database. It fundamentally determines in which manner data can be stored, organized and manipulated. The most popular example of a database model is the relational model, which uses a table-based format.

Language Integrated Query is a Microsoft .NET Framework component that adds native data querying capabilities to .NET languages, originally released as a major part of .NET Framework 3.5 in 2007.

Microsoft SQL Server is a proprietary relational database management system developed by Microsoft. As a database server, it is a software product with the primary function of storing and retrieving data as requested by other software applications—which may run either on the same computer or on another computer across a network. Microsoft markets at least a dozen different editions of Microsoft SQL Server, aimed at different audiences and for workloads ranging from small single-machine applications to large Internet-facing applications with many concurrent users.

A hierarchical query is a type of SQL query that handles hierarchical model data. They are special cases of more general recursive fixpoint queries, which compute transitive closures.

The MySQLi Extension is a relational database driver used in the PHP scripting language to provide an interface with MySQL databases.

Java Database Connectivity (JDBC) is an application programming interface (API) for the Java programming language which defines how a client may access a database. It is a Java-based data access technology used for Java database connectivity. It is part of the Java Standard Edition platform, from Oracle Corporation. It provides methods to query and update data in a database, and is oriented toward relational databases. A JDBC-to-ODBC bridge enables connections to any ODBC-accessible data source in the Java virtual machine (JVM) host environment.

A full table scan is a scan made on a database where each row of the table is read in a sequential (serial) order and the columns encountered are checked for the validity of a condition. Full table scans are usually the slowest method of scanning a table due to the heavy amount of I/O reads required from the disk which consists of multiple seeks as well as costly disk to memory transfers.

The syntax of the SQL programming language is defined and maintained by ISO/IEC SC 32 as part of ISO/IEC 9075. This standard is not freely available. Despite the existence of the standard, SQL code is not completely portable among different database systems without adjustments.

References

  1. ↑ Beaulieu, Alan (2020). "Chapter 1. A Little Background". Learning SQL, 3rd Edition (3rd ed.). O'Reilly Media. ISBN   9781492057611. OCLC   1138944140.
  2. 1 2 Database Fundamentals (PDF) (1st ed.). IBM Corporation. 2010. pp. 122–123.


This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.