Question

I have a MySQL table, in which I will be storing the email_id of a user along with the user’s followers’ email_ids. Its columns are:

ID, USER_EMAIL, FOLLWING_EMAIL

Now while the user is logged in to his account, I want to calculate:

1. The number of people he is following
2. The number of followers he has

Calculating the number of people he’s following is simple:

select count(*) from list where user_email = <logged-in email>

But how can I calculate how many people are following him in just one query?

Answer 1

SELECT
    COUNT(CASE WHEN user_email = '<email>' THEN 1 ELSE NULL END) AS following_cnt,
    COUNT(CASE WHEN following_email = '<email>' THEN 1 ELSE NULL END) AS follower_cnt
FROM
    list
WHERE 
    '<email>' IN (user_email, following_email)