RANK and DENSE_RANK.

With equal values ROW_NUMBER still hands out different numbers. RANK and DENSE_RANK give equal values the SAME rank. They differ after a tie: RANK skips (1, 1, 3), DENSE_RANK does not (1, 1, 2). Use RANK for "competition" ranking, DENSE_RANK for gap-free levels ("the second highest price").

Careful: equality depends on the columns in OVER (ORDER BY ...). If you add a unique second key (id) inside OVER itself, every row becomes distinct and RANK behaves like ROW_NUMBER — equal values are no longer equal. Put a tie-breaker only in the final ORDER BY of the query for a predictable display, and keep it out of OVER when you want ties.

With PARTITION BY, ranking runs separately in each group (for example per category). A NULL key forms its own group — filter it out if you do not want it.

Common mistakes: id inside OVER for RANK/DENSE_RANK; mixing up the two functions; filtering the rank in the same SELECT; ranking in the wrong direction (ASC/DESC).

Small example:

SELECT name, price, RANK() OVER (ORDER BY price DESC) AS price_rank FROM products;