SQL Nested AND/OR Practice Exercises

Why nesting matters

As a reminder, AND binds more tightly than OR — SQL evaluates every AND pair before it looks at the surrounding ORs. The moment you combine an OR choice with an AND condition, you need parentheses to group the OR so it's evaluated as a single unit first.

-- Fruit or Vegetable sales, where quantity is over 10
SELECT *
FROM grocery_store_sales
WHERE (category = 'Fruit' OR category = 'Vegetable')
  AND quantity > 10;

The parentheses group the two category options into one unit. SQL evaluates that group first, then applies AND quantity > 10 to the result — exactly the logic intended.

Combining two OR groups with AND

Nesting isn't limited to one group — you can combine multiple parenthesized OR groups with AND to express more specific logic, such as "one of these categories, and one of these conditions."

-- Electronics or Appliances, where stock is low OR the unit cost is high
SELECT *
FROM product_inventory
WHERE (category = 'Electronics' OR category = 'Appliances')
  AND (stock_quantity < 20 OR unit_cost > 100);

Each parenthesized group is evaluated on its own first. The outer AND then requires both groups to be true — one category match, and at least one of the two numeric conditions.

NOT with parentheses

NOT applies to everything inside the parentheses that follow it — not just the first condition. This is a common trip-up: NOT (A OR B) excludes rows matching either A or B, not just A.

-- Anything that is NOT a Standard or Economy room
SELECT *
FROM hotel_room_bookings
WHERE NOT (room_type = 'Standard' OR room_type = 'Economy');

Without the parentheses, NOT room_type = 'Standard' OR room_type = 'Economy' would mean something different — the NOT would apply only to the first comparison, not the second.

Grouping three or more values

An OR group can hold more than two options. Once a group has three or more equality checks on the same column, it's often cleaner to rewrite it with IN — but the nested OR form works identically.

-- Comedy, Drama, or Animation, at $3 or less
SELECT *
FROM movie_rentals
WHERE (genre = 'Comedy' OR genre = 'Drama' OR genre = 'Animation')
  AND rental_price <= 3;

Common mistakes

Only parenthesizing one OR group when there are two — if you have two separate OR clusters joined by AND, both need their own parentheses, not just the first one.

Assuming NOT only applies to the next condition — NOT in front of a parenthesized group applies to the entire group's result, not just the first comparison inside it.

Misplacing a parenthesis — moving even one parenthesis can silently change which conditions get grouped together, and SQL won't warn you; it will just return the wrong rows.

Over-nesting when IN would do — three or more ORs comparing the same column to different values can usually be replaced with a single IN (...) list, which is easier to read and just as correct.