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 | +-------------+------------+
Explaination:
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.
[Database]