Question 280329 in Mysql Question posted in
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Mysql – How would I create a query to find the employee who has mentored more than 2 people

Employee Table

New to MYSQL. I’m trying to create a query that essentially selects employees who have mentored more than 2 people. The mentored_by column uses the SSN of employee’s to tell who has mentored who, So you can see that that a couple of the SSNs in the SSN column match some of the SSNs in the mentored_by column. (Ignore the one value is that is null because I simply made it that he didn’t have a mentor).

How would I go about creating a query where it selects employees who have mentored more than 2 people (aka if theres the same SSN in multiple rows in mentored_by column)

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2

Answers


  1. 0

    Something like this, I presume:

    select ssn
from emp
group by ssn
having count(distinct mentored_by) > 2;
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  2. 0

    Aggregate your data per mentor and count. With the found mentors select their rows from the employee table.

    select *
from employees
where ssn in
(
  select mentored_by
  from employees
  group by mentored_by
  having count(*) > 2
);

    For your sample data, you will get the first row (Henry), because he mentored three persons (Jennie, Harold, Jameson).

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