You are trying to join to tables without a common key. 
This can be achieved by calculating a ROW_NUMBER() for each row, and joining the two DEs on rowNumber. This isn't random yet but will keep the order of both DEs.

So:
If you only need to perform this once, you could randomize one of your DEs by creating a Data Extension of type "random", "splitting" it into resulting DE with 100% of records, which will physically randomize the order of rows. 

then you can just run this.

```

SELECT 
sub1.fieldInDE1
,sub2.fieldInDE2 
FROM (
   SELECT deOne.fieldInDE1,
          ROW_NUMBER() OVER (ORDER BY deOne.fieldInDE1) AS rn
   FROM myTable1 deOne
   ) AS sub1
INNER JOIN  (
   SELECT fieldInDE2,
          ROW_NUMBER() OVER (ORDER BY fieldInDE2) AS rn
   FROM myTable2 deTwo
   ) AS sub2
ON sub1.rn = sub2.rn
````

If you need to do this regularly or want to have it as pure SQL, then combine the above with an `ORDER BY NEWID()` in one of the tables, which will randomize one of the DEs on-the-fly:

```
SELECT 
sub1.fieldInDE1
,sub2.fieldInDE2 
FROM (
   SELECT deOne.fieldInDE1,
          ROW_NUMBER() OVER (ORDER BY deOne.fieldInDE1) AS rn
   FROM myTable1 deOne
   ) AS sub1
INNER JOIN  (
   SELECT deTwo.fieldInDE2,
          ROW_NUMBER() OVER (ORDER BY NEWID()) AS rn
   FROM myTable2 deTwo
   ) AS sub2
ON sub1.rn = sub2.rn