How is top-n analysis performed?

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How is top-n analysis performed?

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Top-n analysis is performed using a top-n analysis query. Following is the structure of a top-n analysis query:

SELECT [column_list], ROWNUM
FROM (SELECT [column_list] FROM table
ORDER BY top-n_column)
WHERE ROWNUM <= n;

A top-n analysis query comprises the following elements:

A subquery or an inline view that generates the sorted list of records, and includes an ORDER BY clause to ensure that the ranking is in the desired order.

An outer (main) query that limits the number of rows in the final result set, and includes the ROWNUM pseudocolumn and a WHERE clause. The ROWNUM assigns a sequential value, starting with 1, to each row returned by the subquery. The WHERE clause limits the number of rows to be displayed.

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