Structured Query Language (SQL) is a powerful language used to manage data in relational databases. It is the most widely used language for managing data in relational databases, and is used by many of the world’s largest companies. SQL is used to create, update, delete, and query data from databases. It is also used to create and manage database objects, such as tables, views, and stored procedures.
SQL was developed in the 1970s by IBM researchers Donald D. Chamberlin and Raymond F. Boyce. It was initially designed as a query language for IBM’s System R relational database management system. The first version of SQL was called SEQUEL (Structured English Query Language). In 1979, the American National Standards Institute (ANSI) adopted the language as the standard for relational databases.
SQL is a declarative language, meaning that it is used to describe the desired result of a query, rather than to specify how to obtain the result. It is a non-procedural language, meaning that it does not require the user to specify the exact steps to be taken to obtain the desired result.
SQL is composed of a set of commands, or statements, that are used to manipulate data in a database. These commands include SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, ALTER, and many others.
SQL is a powerful language that allows users to perform complex queries on databases. It is highly flexible, allowing users to specify the data they want to retrieve in a variety of ways. For example, users can use the SELECT statement to retrieve data from multiple tables, or to join data from multiple tables.
SQL also supports data manipulation, allowing users to add, modify, or delete data from a database. It also supports data definition, allowing users to create and modify database objects, such as tables, views, and stored procedures.
The following example shows how to use the SELECT statement to retrieve data from a database:
SELECT *
FROM customers
WHERE state = 'CA';
This statement will retrieve all data from the customers table where the state is equal to 'CA'.
SQL has many advantages. It is a powerful language that allows users to perform complex queries on databases. It is also highly flexible, allowing users to specify the data they want to retrieve in a variety of ways. Additionally, SQL is a standard language, meaning that it is supported by most relational databases.
However, SQL also has some drawbacks. It is not a procedural language, meaning that users must specify the desired result, rather than the exact steps to be taken to obtain the result. Additionally, SQL is not well-suited for certain tasks, such as data mining or machine learning.
SQL is related to other database languages, such as PL/SQL and Transact-SQL. PL/SQL is a procedural language that is used to create stored procedures and functions in Oracle databases. Transact-SQL is a procedural language that is used to create stored procedures and functions in Microsoft SQL Server databases.
SQL is not limited to relational databases. It can also be used to query non-relational databases, such as NoSQL databases. Additionally, SQL can be used to query data from flat files, such as CSV files.
SQL is a powerful language that is used to manage data in relational databases. It is the most widely used language for managing data in relational databases, and is used by many of the world’s largest companies. SQL is used to create, update, delete, and query data from databases. It is also used to create and manage database objects, such as tables, views, and stored procedures.