You have to specify if you only want unique opens -- otherwise, _Opens reflects every open of an email by a subscriber:
o.SubscriberKey as 'EMAIL'
, o.eventdate as 'Data_abertura'
You would need to find the foreign key(s) that correctly matches each row in the two DEs for this task.
As @MateuszDabrowski stated, INSERT INTO, etc. are not acceptable, only queries via SELECT. To this extent you need to use a JOIN in your SQL Query to accomplish this.
To that extent, you would want something like the following:
As you want to use a query for that, you can do it with a simple join:
FROM DataExtension2 AS de2
LEFT JOIN DataExtension1 AS de1
ON de1.EmailName = de2.EmailName
However, I wouldn't recommend doing it that way, as it would require ...