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Editorial Team
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Asked: 2026-06-09T16:22:21+00:00

I had to implement the following into my database: The activities that users engage

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I had to implement the following into my database:

  • The activities that users engage in. Each activity can have a name with up to 80 characters, and only distinct activities should be stored. That is, if two different users like “Swimming”, then the activity “Swimming” should only be stored once as a string.

  • Which activities each individual user engages in. Note that a user can have more than one hobby!

So I have to implement tables for this purpose and I must also make any modifications to existing tables if and as required and implement any keys and foreign key relationships needed.

All this must be stored with minimal amount of storage, i.e., you must choose the appropriate data types from the MySQL manual. You may assume that new activities will be added frequently, that activities will almost never be removed, and that the total number of distinct activities may reach 100,000.

So I already have a ‘User’ table with ‘user_id’ as my primary key.

MY SOLUTION TO THIS:
Create a table called ‘Activities’ and have ‘activity_id’ as PK (mediumint(5) ) and ‘activity’ as storing hobbies (varchar(80)) then I can create another table called ‘Link’ and use the ‘user_id’ FK from user table and the ‘activity_id’ FK from the ‘Activities’ table to show user with the activities that they like to do.

Is my approach to this question right? Is there another way I can do this to make it more efficient?

How would I show if one user pursues more than one activity in the foreign key table ‘Link’?

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1 Answer

  1. Editorial Team

    Your idea is the correct, and only(?) way.. it’s called a many to many relationship.

    Just to reiterate what you’re proposing is that you’ll have a user table, and this will have a userid, then an activity table with an activityid.

    To form the relationship you’ll have a 3rd table, which for performance sake doesn’t require a primary key however you should index both columns (userid and activityid)

    In your logic when someone enters an activity name, pull all records from the activity table, check whether entered value exists, if not add to table and get back the new activityid and then add an entry to the user_activity table linking the activityid to the userid.

    If it already exists just add an entry linking that activity id to the userid.

    So your approach is right, the final question just indicates you should google for ‘many to many’ relationships for some more info if needed.

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