SQL (Structured Query Language) is a standardized programming language used for managing and manipulating relational databases. It is the most widely used language for database management and is essential for anyone working with data.

1. Relational Databases:

   • A relational database is a type of database that stores data in tables, which are organized into rows and columns.
   • Each table represents a different entity (e.g., customers, orders) and each row in a table represents a single record.

2. SQL Language:

   • SQL is used to perform various operations on the data stored in relational databases.
   • It includes commands for querying data, updating data, inserting data, and deleting data.

3. Standardization:

   • SQL is standardized by organizations such as the American National Standards Institute (ANSI) and the International Organization for Standardization (ISO).
   • Despite the standardization, different database systems (e.g., MySQL, PostgreSQL, SQL Server) may have slight variations in their SQL implementations.

1. Data Querying:

   • The SELECT statement is used to query data from a database.
   • Example:

     SELECT * FROM customers;
     

     This query retrieves all columns from the customers table.

2. Data Insertion:

   • The INSERT statement is used to add new records to a table.
   • Example:

     INSERT INTO customers (name, email) VALUES ('John Doe', '[email protected]');
     

3. Data Updating:

   • The UPDATE statement is used to modify existing records in a table.
   • Example:

     UPDATE customers SET email = '[email protected]' WHERE name = 'John Doe';
     

4. Data Deletion:

   • The DELETE statement is used to remove records from a table.
   • Example:

     DELETE FROM customers WHERE name = 'John Doe';
     

Let's consider a simple example to illustrate how SQL works. Suppose we have a table named employees with the following structure:

To retrieve all employees who are Developers, we can use the following SQL query:

To add a new employee to the employees table, we can use:

To update the salary of an employee named Bob, we can use:

To remove an employee named Charlie from the table, we can use:

Task: Write an SQL query to retrieve all records from a table named products.

Solution:

Task: Write an SQL query to insert a new product into the products table with the following details: name = 'Laptop', price = 1200.

Solution:

Task: Write an SQL query to update the price of the product named 'Laptop' to 1300.

Solution:

Task: Write an SQL query to delete the product named 'Laptop' from the products table.

Solution:

In this section, we introduced SQL and its importance in managing relational databases. We covered the basic operations of querying, inserting, updating, and deleting data using SQL. These fundamental concepts form the foundation for more advanced SQL topics that we will explore in subsequent modules.