SQL DELETE – Geek Slack

Getting Started with SQL Server

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SQL DELETE Statement

The DELETE statement is used to delete existing records in a table.

Basic Syntax:

DELETE FROM table_name
WHERE condition;

Example 1: Deleting a Single Record

DELETE FROM employees
WHERE employee_id = 101;

This query deletes the record of the employee with employee_id 101.

Example 2: Deleting Multiple Records

DELETE FROM employees
WHERE department = 'Sales';

This query deletes all records of employees who belong to the ‘Sales’ department.

Example 3: Deleting All Records

DELETE FROM employees;

This query deletes all records in the “employees” table. Note: Use this with caution as it will remove all data from the table.

Example 4: Deleting Records with JOIN

DELETE e
FROM employees e
JOIN departments d ON e.department_id = d.department_id
WHERE d.department_name = 'HR';

This query deletes all employee records where the department name is ‘HR’ by joining the employees and departments tables.

Example 5: Using Subqueries in DELETE

DELETE FROM employees
WHERE department_id IN (SELECT department_id FROM departments WHERE location = 'New York');

This query deletes all employee records where the department is located in ‘New York’ by using a subquery.

Important Considerations:

Always use the WHERE clause to specify which records should be deleted. Omitting the WHERE clause will result in all records in the table being deleted.
Back up your data before performing delete operations to prevent accidental data loss.

The DELETE statement is a crucial tool for managing data in your database. Proper usage ensures that unwanted records are removed without affecting the integrity of your data.