Structured Query Language, commonly known as SQL, is a programming language used to manage and manipulate data stored in relational databases. Developed by IBM in the 1970s, SQL is now the standard language for managing and querying data in relational database management systems (RDBMS). SQL is an essential tool for managing data for many organizations, including businesses, governments, and educational institutions. In this article, we will provide an in-depth overview of SQL, including its history, syntax, and applications.
History of SQL
In the early 1970s, IBM researcher Edgar F. Codd developed the concept of a relational database management system (RDBMS). A relational database is a type of database that organizes data into one or more tables, each consisting of rows and columns. The columns represent attributes or characteristics of the data, while the rows represent individual instances of the data. For example, a table might represent a list of customers, with each row representing a single customer and each column representing a characteristic such as name, address, or email address.
Codd's work led to the development of the Structured Query Language, or SQL, as a way to manipulate and retrieve data from relational databases. The first implementation of SQL was developed by IBM in 1974, and it was called System R. In 1979, the first commercial implementation of SQL was released by Relational Software, Inc., which later became Oracle Corporation.
SQL became a standard in 1986 when the American National Standards Institute (ANSI) released a standard for SQL, called SQL-86. Since then, several versions of the SQL standard have been released, including SQL-89, SQL-92, SQL:1999, SQL:2003, and SQL:2016. Although each version of the standard adds new features and functionality, SQL-92 is the most widely used version of the standard.
Syntax of SQL
SQL has a relatively simple syntax that is easy to learn and understand. SQL statements are used to manipulate data in relational databases. The most common SQL statements are:
SELECT: Used to retrieve data from one or more tables.
INSERT: Used to insert new data into a table.
UPDATE: Used to modify existing data in a table.
DELETE: Used to delete data from a table.
SELECT Statement
The SELECT statement is the most commonly used SQL statement. It is used to retrieve data from one or more tables in a database. The basic syntax of a SELECT statement is:
SELECT column1, column2, ... FROM table_name;
This statement retrieves all the columns from the specified table. If you want to retrieve specific columns, you can list them after the SELECT keyword, separated by commas.
For example, to retrieve the name and address columns from a table called Customers, you would use the following statement:
SELECT name, address FROM Customers;
You can also use the SELECT statement with various functions, such as COUNT, SUM, AVG, and MAX, to retrieve summary information about data in a table. For example, to retrieve the number of customers in the Customers table, you would use the following statement:
SELECT COUNT(*) FROM Customers;
INSERT Statement
The INSERT statement is used to insert new data into a table. The basic syntax of an INSERT statement is:
INSERT INTO table_name (column1, column2, ...) VALUES (value1, value2, ...);
This statement inserts a new row into the specified table. The column names are listed after the table name, and the values to be inserted are listed after the VALUES keyword, separated by commas.
For example, to insert a new customer named John Smith with an address of 123 Main Street into the Customers table, you would use the following statement.
INSERT INTO Customers (name, address) VALUES ('John Smith')
0 Comments