Sqlite - efficient select count query

I have a table in my database I do a Select all on:

SELECT * FROM TableA;

I want to append a column that is true or false if there's a related column in anther table. I can do it with this:

SELECT *, (SELECT COUNT(Id) > 0 FROM TableB WHERE Id = TableA.Id) FROM TableA;

But I don't want to have to count EVERY row in TableB to work this out as its ineffient. I essentially want an EXISTS check instead of count. How do I replace the COUNT with EXISTS?

Thanks!