I have a very large table, 25+ Million records.

I need to create a new table from it where three fields are unique.

I tried

```
SELECT Field1,Field2,Field3, Count(*) FROM `Table`  group by Field1,Field2,Field3 having Count(*)>1

```

I get err- out of memory from Mysql

Is there a more efficient way of finding all the unique records with those fields with a count > 1 so I can work with them further (create a new table, etc)?