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Java-based LeetCode algorithm problem solutions, regularly updated

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1729\. Find Followers Count

Easy

SQL Schema

Table: `Followers`

    +-------------+------+
    | Column Name | Type |
    +-------------+------+
    | user_id     | int  |
    | follower_id | int  |
    +-------------+------+
    (user_id, follower_id) is the primary key for this table.
    This table contains the IDs of a user and a follower in a social media app where the follower follows the user.

Write an SQL query that will, for each user, return the number of followers.

Return the result table ordered by `user_id`.

The query result format is in the following example.

**Example 1:**

**Input:**

    Followers table:
    +---------+-------------+
    | user_id | follower_id |
    +---------+-------------+
    | 0       | 1           |
    | 1       | 0           |
    | 2       | 0           |
    | 2       | 1           |
    +---------+-------------+

**Output:**

    +---------+----------------+
    | user_id | followers_count|
    +---------+----------------+
    | 0       | 1              |
    | 1       | 1              |
    | 2       | 2              |
    +---------+----------------+

**Explanation:**

The followers of 0 are {1}

The followers of 1 are {0}

The followers of 2 are {0,1}