Joining a table with itself vs using Group By MySQL

Question

Here is a simplified version of my table:

It contains the columns employee_id column2 column3 xy and they are all NUMERIC

I am having trouble writing a complicated MySQL query. I want to get all the employeeid and column3 values for all employees that have the same value in column2 as another employee and have DIFFERENT values for x and y PAIR from every other employee. For example, if the following 4 rows were in table:

2 100 123.456 5 7
1 234 123.456 5 7
3 100 456.789 5 10
4 100 123.456 5 7

The rows 2 100 123.456 5 7 and 3 100 456.789 5 10 should be obtained because they have different employee ids ( 2 vs 3 ), the same value for column2 ( 100 and 100 ), and different x , y pair: (Employee 2 has x = 5 and y = 7, which is distinct from x = 5 and y = 10).

How can I compare the documents of table with other documents within itself?

Answer 1

SELECT e1.*
FROM employee e1
JOIN employee e2
  ON e1.employee_id <> e2.employee_id  
 AND e1.column2 = e2.column2 
 AND e1.X <> e2.X
 AND e1.Y <> e2.Y

But I guess your last condition should be

AND (e1.X <> e2.X OR e1.Y <> e2.Y)