Most likely you don't mean that you want to join (create) a single table from those tables. Do you want to create a result set based on them. If that is the case, as Sandeep pointed out, you need a join.
So to select a single result set, your query could look something like:
FROM StudentCode sc
INNER JOIN Names n ON n.StudentId = sc.StudentId
INNER JOIN Marks m ON m.StudentId = sc.StudentId