How to add a row for all the rows in another table in SQL Server

I am not the best at the SQL language. I have a table with approximately 20,000 users (rows) in it. I have another table, that I would like to add a row to for every user, using their username. Is this possible using only SQL?

I could just go into the application (written in c#) and use linq to pull out all the users, iterate over them, and add a row for each user. I'm just curious if there is a way to do it in SQL directly.

TABLE Users
Username (varchar)
etc
etc

TABLE ChatChannels
Username (varchar)
ChannelName 开发者_开发知识库(varchar)

I would like to add one row in ChatChannels for every user in Users, using the username to populate the Username column in ChatChannels.

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insert into chatchannels (Username, ChannelName)
select username, 'NewChatChannel'
from users

This inserts one row per username in users, with the channelname set to 'NewChatChannel'.