Updating and Deleting Data in SQL Server

SQL Server provides powerful commands to update and delete data in tables. In this guide, we'll explore how to modify existing data and remove unwanted data from SQL Server tables, covering basic and common scenarios for data manipulation.

Updating Data with the UPDATE Statement

The UPDATE statement is used to modify existing data in a table. Its basic syntax is as follows:

-- Update data in a table
UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;
    

Replace "table_name" with the name of the table you want to update, specify the columns and new values in the SET clause, and use the WHERE clause to specify which rows to update based on a condition.

Example 1: Updating a Single Record

To update a single record in a table, you can use the following SQL code:

-- Update the salary of an employee with EmployeeID = 101
UPDATE employees
SET salary = 55000
WHERE EmployeeID = 101;
    

Example 2: Updating Multiple Records

If you want to update multiple records simultaneously, you can use a single UPDATE statement with a condition that matches multiple rows:

-- Update salaries for all employees with a salary below 50000
UPDATE employees
SET salary = salary * 1.1
WHERE salary < 50000;
    

Deleting Data with the DELETE Statement

The DELETE statement is used to remove data from a table. Its basic syntax is as follows:

-- Delete data from a table
DELETE FROM table_name
WHERE condition;
    

Replace "table_name" with the name of the table you want to delete data from, and use the WHERE clause to specify which rows to delete based on a condition.

Example: Deleting Records

To delete records that match a specific condition, you can use the DELETE statement as follows:

-- Delete all employees with a salary below 40000
DELETE FROM employees
WHERE salary < 40000;
    

Best Practices for Data Modification

When updating and deleting data in SQL Server, it's crucial to follow best practices to maintain data integrity and perform these operations safely. This includes taking precautions, using transactions, and handling errors effectively.

What's Next?

You've learned how to update and delete data in SQL Server, essential skills for managing and maintaining databases. As you continue your SQL journey, you can explore more advanced topics such as database design, transactions, and optimizing database performance.

Stay curious and keep practicing your SQL skills to become proficient in working with SQL Server databases.