在大表上使用循环更新批处理

I have two tables with overlaping data. One table is about 90% duplicate of the other. I need to identify the 10% of unique records in a table and move it to it's parent table. Both of these tables are 400 million + rows with 300+ columns. The method I am attempting is adding a flag field to uniquely ID the records I need to transfer however I need to update the field and am struggling with the logic. Below is what I have put together so far and it causes a never ending loop. There are no null values in either table.I have two tables with overlaping data. One tab