What's the difference between saying: I'm having dinner with a friend tomorrow and i

[B45]

What's the difference between saying:

I'm having dinner with a friend tomorrow and it's not a date or anything so you are more than welcome to join.

Vs


I'm having dinner with a friend tomorrow and it's not a date or anything so you are more than welcome to join us.

Are both okay and grammatical?

 

[Raymott]

The first lacks an object of 'join'.

 

[B45]

Therefore, only the second one is correct. Right?

 

[Raymott]

Yes.
You can say, "I'm forming a club/party. Would you like to join?"
But if you're asking someone to join you for dinner, you need to say "Would you like to join us/me". Parties and clubs are things that people generally join, but dinners are not.