MySQL — Update

Basic UPDATE

UPDATE users SET name = 'Jane' WHERE id = 1;

Update Multiple Columns

UPDATE users
SET name = 'Jane', email = 'jane@example.com'
WHERE id = 1;

Update All Rows

UPDATE users SET is_active = TRUE;

UPDATE Examples

-- Update single row
UPDATE products
SET price = 799.99
WHERE id = 1;

-- Update multiple rows
UPDATE products
SET stock = stock - 1
WHERE category = 'Electronics';

-- Update with condition
UPDATE users
SET is_active = FALSE
WHERE last_login < '2023-01-01';

-- Update using other columns
UPDATE products
SET price = price * 1.10
WHERE category = 'Premium';

UPDATE with LIMIT

-- Update first 5 rows
UPDATE users
SET is_active = FALSE
WHERE last_login < '2023-01-01'
LIMIT 5;

WARNING

-- Always use WHERE clause!
UPDATE users SET is_active = FALSE; -- Updates ALL rows!

-- Test with SELECT first
SELECT * FROM users WHERE condition;

Mini Practice

Write MySQL code that:

1. Updates a single row
2. Updates multiple columns
3. Updates with conditions
4. Tests with SELECT before update

Up Next

Next: Learn about Deleting Data.