You won't get any rows because that query won't run: you will get an error message from SQL Server that
"Column 'e.manager_id' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause."
And even if it did, it's wouldn't produce what you wanted because a basic SELECT from two tables produces all combinations of those tables.
Assume you have two tables, TableA and TableB Each has one column (TableA.A and TableB.B) and each have two rows:
TableA:
A1
A2
TableB:
B1
B2
A simple SELECT query with both tables will give you four rows:
SELECT A.A, B.B FROM TableA A, TableB B
A1 B1
A2 B1
A1 B2
A2 B"
Because SQL doesn't know any better, so it tried hard to give you what you want.
GROUP BY won't reduce that because you will get the error message I mentioned above: GROUP BY is there to aggregate values, not combine tables!
See here:
SQL GROUP By and the "Column 'name' is invalid in the select list because..." error[
^]
Instead, what you need to do is JOIN tables together:
SQL Joins[
^]