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SQL DELETE

The DELETE statement is used to remove one or more rows from a table.

🔹 Basic Syntax

DELETE FROM table_name
WHERE condition;

⚠️ Always use a WHERE clause to avoid deleting everything!

🔹 Examples

-- Delete a specific employee
DELETE FROM employees
WHERE employee_id = 101;

-- Delete all employees from the IT department
DELETE FROM employees
WHERE department = 'IT';

🔹 Delete All Rows (Be Cautious!)

-- Delete all rows (but keep the table)
DELETE FROM employees;

-- Oracle tip: Use TRUNCATE for faster delete (no WHERE allowed)
TRUNCATE TABLE employees;

🔹 With Subqueries

-- Delete employees who are not assigned to any department
DELETE FROM employees
WHERE department_id NOT IN (
  SELECT id FROM departments
);

🧠 Quick Recap

ActionSyntax Example
Delete with conditionDELETE FROM table WHERE ...
Delete all rowsDELETE FROM table;
Fast delete (Oracle)TRUNCATE TABLE table_name;
Delete using subqueryDELETE WHERE col IN (SELECT ...)

✅ Use DELETE to clean up data—carefully!

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