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 SQL Definition & Overview      [Return To Index] Jump to:  
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Term: SQL

Definition:
SQL stands for Structured Query Language. It is the standard RDBMS language which contains a formal set of statements and commands to interact with the database. It can be used to fetch and manipulate data by using the statements as commands to the database engine. SQL statements accomplish variety of tasks such as creating database objects, monitoring database access, and ensuring database security.

The SQL language was originally based upon relational algebra and calculus.

With the growing demands of applications and support, Oracle regularly provides enhancements to traditional SQL to meet the needs of database professionals. Some of them are, for example, LOB support and XML support.

The SQL language is subdivided into several language elements, which include:

  1. Clauses, which are components of statements and queries.
  2. Expressions, which can return either scalar values or tables consisting of columns and rows of data.
  3. Predicates, which specify the conditions that can be evaluated to SQL three-valued logic (3VL) or Boolean (true/false/unknown) truth values. These are are used to limit or restrict the effects of statements and queries, or to change program flow.
  4. Queries, which retrieve data based on specific criteria.
  5. Statements, which may have a persistent effect on schemas and data, or which may control transactions, program flow, connections, sessions, or diagnostics.

These SQL language constructs define the capabilities of SQL in the database:
  1. SELECT, INSERT, UPDATE, and DELETE (Query statements)
  2. Data Definition Language (DDL)
  3. Data Manipulation Language(DML)
  4. Transaction Control Language(TCL)
  5. Data Control Language(DCL)

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