SQL：如何连接具有相同含义但列名不同的表？

Question

Say I have table student, and table advisor. student contains ID and name:

+----+------+
| ID | name | 
+----+------+

advisor contains s_id and i_id:

+------+------+
| s_id | i_id | 
+------+------+

how to join with result like this:

+----+------+------+
| ID | name | i_id | 
+----+------+------+

I've tried

select *
from student join advisor on student.ID=advisor.s_id

But it returns

+----+------+------+------+
| ID | name | i_id | s_id |
+----+------+------+------+

Thanks!

Answer 1

Modify your existing query by including in the select list only the columns you actually want to see:

SELECT s.ID, s.name, a.i_id
FROM student s
INNER JOIN advisor a
    on s.ID = a.s_id;

In case a given student might actually have no advisors, you could use a left join here to report NA for that student:

SELECT s.ID, s.name, COALESCE(a.i_id, 'NA') AS i_id
FROM student s
LEFT JOIN advisor a
    on s.ID = a.s_id;