How to Find the Most Frequent Food ID per Country in SQL?

Finding the Most Common Value for a Column Given Another Column's Value in SQL

In a scenario where a table contains multiple columns, such as "country", "food_id", and "eaten", a common task is to determine the most frequently occurring value for one column ("food_id") within each unique value of another column ("country").

One approach, as mentioned in the question, involves creating temporary tables and performing multiple subqueries to calculate the counts, find the maximum count, and retrieve the corresponding "food_id" values. While functional, this method can seem cumbersome.

Fortunately, PostgreSQL 9.4 introduced a more straightforward solution: the mode() function. This function provides an efficient way to find the most common value for a specified column within each group defined by a grouping expression.

To employ the mode() function for this task, the following SQL query can be used:

SELECT mode() within group (order by food_id)
FROM munch
GROUP BY country

This query leverages the mode() function to calculate the most common "food_id" value for each unique "country" value. The WITHIN GROUP (ORDER BY food_id) clause ensures that the mode() function operates on the "food_id" column within each country group, ranking the values in ascending order before identifying the mode.

The result of this query, as also demonstrated in the provided answer, will be a table displaying the "country" and its corresponding most common "food_id" value:

country | mode
--------------
GB      | 3
US      | 1

The above is the detailed content of How to Find the Most Frequent Food ID per Country in SQL?. For more information, please follow other related articles on the PHP Chinese website!