How Can I Limit the Number of Skills Shown in a GROUP_CONCAT Query to the Top Three?

GROUP_CONCAT with Skill Limit

In a database with players and their skills in a many-to-many relationship, a query is needed to list players and their top three skills. The initial query attempts to use GROUP_CONCAT to concatenate skill titles, but it lacks a way to limit the number of skills to three.

Solution:

While GROUP_CONCAT does not directly support a limit, a workaround can be used by post-processing the concatenated string:

substring_index(group_concat(s.title SEPARATOR ','), ',', 3) as skills

This command extracts the first three skill titles separated by commas from the concatenated string. It assumes that skill names do not contain commas and that the number of skills is reasonably small.

Note:

To ensure correct results, the player_skills table should have a primary key consisting of the tuple (player_id, skill_id), preventing the same skill from being assigned to a player multiple times.

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