Last Updated: 15 Aug, 2021
Second Degree Follower
Hard
Asked in company
In facebook, there is a follow table with two columns: followee, follower.
Please write a sql query to get the amount of each follower’s follower if he/she has one.
For example:
+-------------+------------+
| followee | follower |
+-------------+------------+
| A | B |
| B | C |
| B | D |
| D | E |
+-------------+------------+
Should output:
+-------------+------------+
| follower | num |
+-------------+------------+
| B | 2 |
| D | 1 |
+-------------+------------+
Explanation:
Both B and D exist in the follower list, when as a followee, B's follower is C and D, and D's follower is E. A does not exist in follower list.
Note:
Followee would not follow himself/herself in all cases.
Please display the result in follower's alphabet order.
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