Question

Is there a way in mysql to check one specific column and see if the value occurs more then one time, and if so get the row.

lets say that my table looks like this:

id | first_name | last_name | age
1     john           doe       20
..    .......       .....     ...
..    .......       .....     ...

So I want the mysql to go and bring back a list where the age is 18 AND where the first_name occurs more then once.

Answer 1

SELECT y.id, y.first_name, y.last_name, y.age
    FROM (SELECT first_name
              FROM YourTable
              WHERE age = 18
              GROUP BY first_name
              HAVING COUNT(*) > 1) t
        INNER JOIN YourTable y
            ON t.first_name = y.first_name
    WHERE y.age = 18;