Filter Results in SQL

Question

Suppose I have a table

  id            value
------        ---------
  10              123
  10              422
  11              441
  11              986
         


        

Answer 1

select a2.*
from MyTable a2
inner join
(
select a1.id
from MyTable a1
group by a1.id
having count(*) > 1
) a3
on a3.id = a2.id

Answer 2

You can use this query :

SELECT * from table where id in 
( SELECT id FROM table group by id having count(id) > 1 )

Answer 3

Assuming a UNIQUE KEY can be formed on (id,value)...

SELECT DISTINCT x.*
           FROM my_table x
           JOIN my_table y
             ON y.id = x.id
            AND y.value <> x.value

If a UNIQUE KEY cannot be formed on (id,value), then this isn't really a table in a strict RDBMS sense.

Answer 4

With mysql 8+ or mariadb 10.2+, you would use the count window function:

select id, value
from (
    select id, value, count(id) over (partition by id) as num_values
    from sometable
) foo
where num_values > 1;