I have a table “Student”, now I would like to query the result as same as the second table, one group must have 2 students. Thanks!!

Question

I have a table “Student”, now I would like to query the result as same as the second table, one group must have 2 students. Thanks!!

Student ID Name Gender Group

1 A M A1

2 B F A1

3 C M A2

4 D M A2

5 E F A3

6 F F A3

Name1 Gender1 Name2 Gender2 Group

A M B F A1

C M D M A2

E F F F A3

Answer 1

Something like:

select t1.name, t1.gender, t2.name, t2.gender, t1.group 
from student t1, student t2 
where t1.group = t2.group and t1.id < t2.id

Answer 2

SELECT s1.name AS Name1, s1.gender AS Gender1, 
       s2.name AS Name2, s2.gender AS Gender2, 
       groups.group_s
FROM (
  SELECT MIN(id) AS st_first, MAX(id) AS st_second, group_s
  FROM students
  GROUP BY group_s
) AS groups
LEFT JOIN students s1 ON groups.st_first=s1.id
LEFT JOIN students s2 ON groups.st_second=s2.id

students is the name of your table and group_s is the group column

Answer 3

Here is the complete example.

CREATE TABLE testing
(id char(10),
name char(10),
gender char(1),
grp char(10))

insert into testing values ('1','A','M','A1')
insert into testing values ('2','B','F','A1')
insert into testing values ('3','C','M','A2')
insert into testing values ('4','D','M','A2')
insert into testing values ('5','E','F','A3')
insert into testing values ('6','F','F','A3')


    select name1, gender1, name2, gender2, a.grp  from
    (
    SELECT name1 = CASE CONVERT(int,id)%2 WHEN 1 THEN name ELSE null END,
            gender1 = CASE CONVERT(int,id)%2 WHEN 1 THEN gender ELSE null END,
            grp FROM testing where CONVERT(int,id)%2 =1
    ) a 
    left join 
    (
    SELECT name2 = CASE CONVERT(int,id)%2 WHEN 0 THEN name ELSE null END,
            gender2 = CASE CONVERT(int,id)%2 WHEN 0 THEN gender ELSE null END,
            grp FROM testing where CONVERT(int,id)%2 =0
    ) b on a.grp=b.grp