sql-server - 如何从更多列中选择但按 1 列分组？

SELECT        studentnum
FROM            Atten
WHERE        (att = 'Yes') AND (unitCode = 'MMA1034')
GROUP BY studentnum
HAVING        (COUNT(*) < 4)

如何选择更多列？例如，student_name 也是？

最佳答案

如果学生信息在 Student 表中，则查询可能如下所示:

SELECT student_name, student_birth_day, studentnum
FROM Student S
RIGHT JOIN (
  SELECT studentnum, count(*) as cnt
  FROM   Attendance
  WHERE (attStatus = 'Yes')
  AND   (unitCode = 'MMA1034')
  GROUP BY studentnum
  HAVING (COUNT(*) < 4)
) A
ON A.studentnum = S.studentnum

关于sql-server - 如何从更多列中选择但按 1 列分组？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/7564285/