Find Followers Count

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Medium

Description

You have a Followers table where each row represents that a user (follower_id) follows another user (user_id). Write a SQL query to find the number of followers for each user. Return the result ordered by user_id ascending. (user_id, follower_id) is the primary key.

Database Schema

Followers

Column Name	Type	Description
user_id	INT	The user being followed
follower_id	INT	The user who follows

Example

Followers

user_id	follower_id
0	1
1	0
2	0
2	1

Output

user_id	followers_count
0	1
1	1
2	2

Explanation:

User 0 is followed by user 1. User 1 is followed by user 0. User 2 is followed by users 0 and 1.

Approach hint

Start with a simple approach, explain the trade-off, then move toward a cleaner or more scalable solution.

Common mistake

Skipping assumptions, edge cases, or trade-offs can make an otherwise good answer feel incomplete.