<aside> ✏️ DML commands work with the data inside tables: INSERT, UPDATE, DELETE.

</aside>

1. INSERT — Add Data

Method 1: Manual INSERT with VALUES

-- Insert multiple rows
INSERT INTO customers (id, first_name, country, score)
VALUES
    (6, 'Anna', 'USA', NULL),
    (7, 'Sam', NULL, 100)

-- Insert a single row
INSERT INTO customers (id, first_name, country, score)
VALUES (8, 'Max', 'USA', 368)

-- Insert without specifying columns (not recommended)
INSERT INTO customers
VALUES (9, 'Andreas', 'Germany', NULL)

-- Insert only specific columns (others will be NULL/default)
INSERT INTO customers (id, first_name)
VALUES (10, 'Sahra')

Method 2: INSERT using SELECT (Copy data between tables)

INSERT INTO persons (id, person_name, birth_date, phone)
SELECT
    id,
    first_name,
    NULL,
    'Unknown'
FROM customers

2. UPDATE — Modify Existing Data

Always use WHERE to avoid updating all rows accidentally.

-- Update a single customer's score
UPDATE customers
SET score = 0
WHERE id = 6

-- Update multiple columns at once
UPDATE customers
SET score = 0,
    country = 'UK'
WHERE id = 10

-- Update all rows where score IS NULL
UPDATE customers
SET score = 0
WHERE score IS NULL

<aside> ⚠️ Without WHERE, UPDATE affects ALL rows in the table!

</aside>

3. DELETE — Remove Data

-- Delete specific rows
DELETE FROM customers
WHERE id > 5

-- Delete all rows (keep the table structure)
DELETE FROM persons

-- Faster way to delete all rows (cannot be rolled back)
TRUNCATE TABLE persons

<aside> 💡 TRUNCATE is faster than DELETE for clearing all rows but cannot be rolled back in most databases.

</aside>

DML vs DDL — Quick Comparison