SQL practice: EXISTS and Correlated Subqueries

Use EXISTS to find customers who ordered at branch 1.

Use NOT EXISTS to find products never sold.

Use NOT EXISTS to find branches with no orders.

Find employees earning above the average salary of their own branch.

Find customers who have at least one Delivered order, using EXISTS.

Find products that cost more than the average price within their own category.

Find employees who have at least one person reporting to them.

Rewrite 17-2 using a LEFT JOIN instead, and confirm you get the same two products.

List employees who don't manage anyone. It returns nothing, even though most employees manage no one. Fix it.