1. It's the same song that I sang last week.


2. It's the same song as I sang last week.

I was told the second one is correct. Why?
What is the difference between using "as" and "that" here?
Could anyone explain me on this?

Thanks in advance.

With regards,
I don't know which one is correct but I would prefer to say:

It's the same song I sang last week.

Anybody please correct me if I am wrong.

Hi Meg2589,
I found this on "How to write and speak better" by Reader's Digest.
Let me know when to use "as" and "that".
I think the examples have been provided on the book to differentiate between using "as" and "that".
Since I'm not a native speaker of English, I feel native speakers are in a better position to answer my question.

With regards,