T-SQL帮助——有人能想出一个基于集合的操作来替换sql中的当前行基操作吗?

I have a question in one of the process, currently it's written in row-based operation, and it takes an hour to populate around 50,000 records but will take over 5 days for 3million records. I have been trying to think of a different approach which involve only set-based tsql and not use row-by-row/cursor, it is the cursor that makes the process super slow, but can't think of any other ways. Can someone help? Here's what I am trying to accomplish, basically I have a table of email addresses which gets updated everyday, and I need to parse out each part and add them to a separate email part table. I have a question in one of the process, curren