Introduction to Structured Query Language

Introduction to Structured Query Language

Structured Query Language (SQL) is a standard language for accessing and manipulating data in relational databases. SQL allows users to perform various operations on data, such as querying, inserting, updating, deleting, creating, and modifying tables, views, indexes, and other database objects. SQL also supports features such as transactions, constraints, triggers, functions, procedures, and user-defined types.

SQL is based on the relational model of data, which organizes data into tables consisting of rows and columns. Each table has a name and a set of attributes (columns) that define the properties of the data. Each row in a table represents a record (or tuple) of data that has values for each attribute. Tables can be related to each other by using keys, which are attributes that uniquely identify a row in a table or link rows from different tables.

SQL consists of several sublanguages, such as Data Definition Language (DDL), Data Manipulation Language (DML), Data Control Language (DCL), and Data Query Language (DQL). DDL is used to create and modify the structure of database objects. DML is used to insert, update, and delete data in database objects. DCL is used to control access and permissions to database objects. DQL is used to query and retrieve data from database objects.

SQL is widely used in various domains and applications, such as business intelligence, data analysis, web development, data warehousing, and more. SQL is supported by many database management systems (DBMS), such as Oracle, MySQL, PostgreSQL, Microsoft SQL Server, SQLite, and more. Each DBMS may have its own extensions and variations of SQL syntax and functionality, but they all follow the core principles and standards of SQL.

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