Introduction to SQL

Welcome to the Microsoft Developer Network (MSDN) documentation for SQL. This section provides a foundational understanding of Structured Query Language (SQL), its purpose, and its fundamental concepts. SQL is a domain-specific language used in programming and designed for managing data held in a relational database management system (RDBMS), or for stream processing in a relational data stream management system (RDSMS).

What is SQL?

SQL stands for Structured Query Language. It's the standard language for interacting with relational databases. Whether you're retrieving data, inserting new records, updating existing ones, or deleting obsolete information, SQL is the tool you'll use.

Key Concepts

Databases: A structured collection of data.
Tables: Databases are organized into tables, which are collections of related data entries. Each table consists of rows and columns.
Rows (Records): Represent a single entry in a table.
Columns (Fields): Represent an attribute of the data.
SQL Commands: Instructions given to the database to perform specific operations.

Why Use SQL?

SQL is powerful, versatile, and widely adopted across various industries. Its declarative nature means you tell the database what you want, not how to get it, allowing the database system to optimize the execution. Key advantages include:

Data Management: Efficiently manage large volumes of data.
Data Retrieval: Powerful querying capabilities to extract specific information.
Data Integrity: Enforce rules to ensure data accuracy and consistency.
Accessibility: A standardized language used by most RDBMS, including SQL Server, MySQL, PostgreSQL, Oracle, and SQLite.

A Simple SQL Example

Here's a basic SQL query to select all records from a table named Customers:


                    SELECT * FROM Customers;

In this example:

SELECT is a command used to retrieve data.
* is a wildcard that means "all columns".
FROM specifies the table from which to retrieve the data.
Customers is the name of the table.
; is a statement terminator (though not always required, it's good practice).

Next Steps

In the following sections, we will delve deeper into specific SQL commands, data types, table creation, and more complex querying techniques. Continue to the SQL Basics section to learn about fundamental SQL operations.