Dense_rank SQL

The `DENSE_RANK()` function in SQL is a window function that assigns a rank to each row within a partition based on the values of one or more columns. It's similar to the `RANK()` function, but it differs in how it handles ties. When multiple rows have the same value in the ranking column, `RANK()` assigns the same rank and skips the next rank. `DENSE_RANK()`, on the other hand, assigns consecutive ranks without gaps. This means that if two rows have the same rank, the next rank is immediately assigned to the following row, maintaining a continuous sequence. This is often preferred for situations where a gap in ranking would be misleading, such as in a leaderboard where you want to see a clear progression of ranks. For example, if three students have the same score, `RANK()` might assign ranks 1, 1, 1, and then 4 to the next student, whereas `DENSE_RANK()` would assign ranks 1, 1, 1, and then 2 to the next student. This makes `DENSE_RANK()` more suitable for situations where a continuous ranking is desired. It's important to understand that `DENSE_RANK()` is a window function, meaning it operates on a set of rows (a partition) and returns a value for each row within that partition. The function is often used in conjunction with other window functions to perform more complex analyses on data.