SQL Tutorial: Insert, Update, Delete, and Alter in SQL

Introduction

In this tutorial, we will focus on the basic SQL operations: Insert, Update, Delete, and Alter.

Insert Statement

The Insert statement is used to add new records to a table. It follows the syntax:

INSERT INTO table_name (column1, column2, ...)
VALUES (value1, value2, ...);

For example, to insert a new record into the “Customers” table:

INSERT INTO Customers (CustomerID, CustomerName, City)
VALUES ('001', 'John Doe', 'New York');

Update Statement

The Update statement is used to modify existing records in a table. It follows the syntax:

UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;

For example, to update the “City” of a customer with a specific “CustomerID” in the “Customers” table:

UPDATE Customers
SET City = 'Los Angeles'
WHERE CustomerID = '001';

Delete Statement

The Delete statement is used to remove records from a table. It follows the syntax:

DELETE FROM table_name
WHERE condition;

For example, to delete a customer with a specific “CustomerID” from the “Customers” table:

DELETE FROM Customers
WHERE CustomerID = '001';

Alter Statement

The Alter statement is used to modify the structure of a table. It can add, modify, or delete columns in an existing table. It follows the syntax:

ALTER TABLE table_name
ADD column_name datatype;

ALTER TABLE table_name
MODIFY column_name datatype;

ALTER TABLE table_name
DROP COLUMN column_name;

For example, to add a new column “Email” to the “Customers” table:

ALTER TABLE Customers
ADD Email VARCHAR(50);

Conclusion

In this tutorial, we covered the basic SQL operations: Insert, Update, Delete, and Alter. These operations are fundamental for managing and manipulating data in a relational database. By understanding and practicing these statements, you will have a solid foundation for working with SQL.

Remember, SQL is a powerful language with many more features and advanced operations. This tutorial serves as a starting point to help you get familiar with the basics.