What is the correct format for implementing a RANK function?

The RANK function is used in databases to assign a rank to each row within a partition of a result set, with ties receiving the same rank. The correct syntax for implementing a RANK function involves using the OVER clause, which specifies the order in which the ranks are assigned to the rows.

In the correct format, the function RANK() is followed by the OVER keyword, which defines the context for the ranking operation. The ORDER BY clause indicates how the rows should be sorted to determine their rank. Using "ORDER BY expr DESC" specifies that the rows should be ranked based on the specified expression in descending order. This means that higher values receive a lower rank number (1 being the highest rank), which is often a common requirement in ranking scenarios.

Thus, the correct format with the RANK function allows for flexibility in defining the ranking criteria, and the use of the OVER clause is essential for its proper functioning. The other choices do not follow the correct syntax or structure for implementing the RANK function in SQL.