How to use Subquery with Row Number In SQL
This method makes use of a subquery that produces a row number (row_num) for each row of its region in accordance with its revenue, i.e. higher revenue rows are assigned lower numbers.
The ROW_NUMBER() function provides an integer representation of each row within the partition defined by the PARTITION BY clause.
SELECT *
FROM (
SELECT *,
ROW_NUMBER() OVER (PARTITION BY region ORDER BY revenue DESC) AS row_num
FROM sales_data
) AS ranked
WHERE row_num <= 2;
Output:
Explanation: This query retrieves all columns from the sales_data table, adds a row number for each region based on revenue in descending order, and then filters the result to only include the top 2 rows for each region.
How to Restrict Results to top N Rows per Group in SQLite?
Assume a situation where the data to be retrieved is grouped by specific criteria and the rows are desired to be filtered so that data from the top N rows in each group can be obtained, SQLite databases will be the tools used.
This can be particularly important where, for example, items need to be ranked categorically or to identify the top performers in different groups. While database systems that offer specialized functions for this task exist, SQLite doesn’t provide such core capabilities.
In this article, We will learn about How to Restrict results to the top N rows per group in SQLite by understanding various methods along with the examples and so on.