根据另一个表中的数据从表中选择行

Question

Mentor table
------------
name (varchar)
contact (int)
english (boolean)
french (boolean)
german (boolean)


Student table
-------------
name (varchar)
contact (int)
english (boolean)
french (boolean)
german (boolean)

I want to match mentor with student based on the languages, such that for example:

if mentor1 knows english and french, he will be matched with all students that know at least english or french.

mentor1 (english, french)
-------------------------
studentA (english); 
studentB (english, french); 
studentC (english, german);
studentD (english, french, german)  

if mentor2 know german only, he will be matched with all students that know at least german. the students matched can know more than just german.

mentor2 (german)
----------------
studentC (english, german)
studentD (english, french, german)

normally i will just use a bunch of if then else to piece together a sql string but i am using gridview to display the data so i am not sure what can i do.

sample codes and tutorials are alway welcome.

edit: forgot to mention that the mentor table will also have columns such as name and contact . so the output on the gridview should be 1 row per mentor .

Answer 1

Select
   m.MentorName
   , m.Language
   , s.StudentName
from Mentor as m
inner join Student as s
on (m.English = 1 and m.English = s.English)
    or (m.french = 1 and m.French = s.French)
    or (m.German = 1 and m.German = s.German);

This would be easier if you had your tables structured without field for each language but a record instead

Table: Mentor(MentorName, Language)
Rows:
Mentor1 | English
Mentor2 | Englisn
Mentor2 | French

Do the same for Students and then the query is:

Select
   m.MentorName
   , m.Language
   , s.StudentName

from Mentor as m
inner join Student as s
on m.Language = s.Language

The benefit here is if you add another language, it is purely data entry and no need to change table structure or your code, but that is not always an option.

Answer 2

SELECT  m.*, s.name
FROM    dbo.Mentor m
JOIN    dbo.Student s
ON EXISTS 
(
    SELECT  x.LanguageID
    FROM    
    (
        SELECT 1 AS LanguageID WHERE s.english = 1 UNION ALL 
        SELECT 2 AS LanguageID WHERE s.french = 1 UNION ALL 
        SELECT 3 AS LanguageID WHERE s.german = 1
    ) x
    INTERSECT
    SELECT  y.LanguageID
    FROM    
    (
        SELECT 1 AS LanguageID WHERE m.english = 1 UNION ALL 
        SELECT 2 AS LanguageID WHERE m.french = 1 UNION ALL 
        SELECT 3 AS LanguageID WHERE m.german = 1
    ) y
)
ORDER BY m.name