Quick Answer

Using UPDATE to change data

Understanding the Issue

The UPDATE statement modifies existing data in table rows. Always use WHERE to target specific rows, unless updating all rows intentionally.

The Problem

This code demonstrates the issue:

Sql Error 
-- Problem: Need to change prices
SELECT * FROM products WHERE category = 'Electronics'; -- Old prices

The Solution

Here's the corrected code:

Sql Fixed 
-- Solution 1: Update specific rows
UPDATE products
SET price = price * 1.1
WHERE category = 'Electronics';

-- Solution 2: Update multiple columns
UPDATE employees
SET salary = salary * 1.05,
    last_raise = CURRENT_DATE
WHERE department = 'Engineering';

-- Solution 3: Update with JOIN
UPDATE orders o
JOIN customers c ON o.customer_id = c.customer_id
SET o.priority = 'High'
WHERE c.vip = 1;

Key Takeaways

Always include WHERE clause unless updating all rows.