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CRUD Operations

INSERT — Create​

-- Insert a single row
INSERT INTO employees (name, email, age, salary)
VALUES ('Alice', 'alice@example.com', 30, 75000);

-- Insert multiple rows
INSERT INTO employees (name, email, age, salary) VALUES
    ('Bob', 'bob@example.com', 25, 60000),
    ('Charlie', 'charlie@example.com', 35, 85000);

SELECT — Read​

-- Select all columns
SELECT * FROM employees;

-- Select specific columns
SELECT name, salary FROM employees;

-- With alias
SELECT name AS employee_name, salary AS annual_salary FROM employees;

-- Distinct values
SELECT DISTINCT department_id FROM employees;

UPDATE — Update​

-- Update specific rows
UPDATE employees
SET salary = 80000
WHERE name = 'Alice';

-- Update multiple columns
UPDATE employees
SET salary = 90000, age = 31
WHERE id = 1;
danger

Always use WHERE with UPDATE — without it, all rows get updated.

DELETE — Delete​

-- Delete specific rows
DELETE FROM employees
WHERE id = 5;

-- Delete all rows (keeps table structure)
DELETE FROM employees;

-- Faster way to delete all rows (resets auto-increment)
TRUNCATE TABLE employees;
danger

Always use WHERE with DELETE — without it, all rows get deleted.