How to add values that aren't in one table to another in different column

[leightx]

I'm trying to compare Table 1 and Table 2 and add Table 2 SKU items that are not found in SKU 1 to the bottom of SKU 2. I tried doing a left anti join (using table 2 as left table) to get the unique Table 2 SKUs, but I can't append them to the SKU2 column in table 1 b/c there is a circular reference. I tried using reference tables for both Table 1 and 2, and still ran into the same problem. 

[kentyler]

I believe the usual pattern is to make 2 temp tables. Extract distinct values from sku 1 into one of them and distinct values from sku 2 into the other. Then make a 3rd table using a union query to combine those 2. You make have to wrap the union statement in another distinct to eliminate duplicate values.

[leightx]

Just to clarify, I can't have only distinct values in SKU2 in the desired output. 

Basically, I want to compare SKU1 (from table 1) and SKU (from table 2) and get the items from SKU (table 2) that are not in SKU1 (table 1). Then I want to append those into the SKU2 column in table 1.