Query
Query is a term used in Computer Science and Information Technology to refer to a request for data or information from a database, which is formulated in a specific syntax. The term is commonly used in the context of Database Management Systems (DBMS), where queries are used to retrieve data that meets certain criteria.
Overview[edit | edit source]
A query is essentially a question, specifically a request for specific data contained in a database. Queries are one of the main methods used to retrieve and manipulate data in a Database. They are usually written in a special language, such as SQL (Structured Query Language), which is designed for managing data held in a Relational Database Management System (RDBMS), or for stream processing in a Relational Data Stream Management System (RDSMS).
Types of Queries[edit | edit source]
There are several types of queries that can be used in a DBMS, including:
- Select Queries: These are the most common type of queries, which retrieve data from a database and display it in a datasheet where you can analyze it.
- Action Queries: These queries can perform operations other than the selection of data. They can be used to create new tables, add data to existing tables, update data, or delete data.
- Parameter Queries: These queries are more dynamic and prompt for input every time they are run.
- Aggregate Queries: These queries return a single value calculated from values in a column.
- SQL Queries: These are queries that are written in SQL. They can be used in all types of databases, not just relational ones.
Query Languages[edit | edit source]
A query language is a type of programming language that is designed to facilitate retrieving specific information from databases. The most widely used query language is SQL. Other query languages include QBE (Query By Example), DMX (Data Mining Extensions), MDX (Multidimensional Expressions), and XQuery.
See Also[edit | edit source]
References[edit | edit source]
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