【sql 練習題 38 ，39】檢索至少選修兩門課程的學生學號，查詢選修了全部課程的學生信息

題目38：檢索至少選修兩門課程的學生學號

 

SELECT studentid ,COUNT(courseid) AS a
FROM student_score GROUP BY studentid HAVING a >=2

 

 

 

 

題目39：查詢選修了全部課程的學生信息

GROUP BY studentid 然后count(score)=全部課程數

 

 

SELECT student.* FROM student,
(SELECT studentid,COUNT(courseid) AS a FROM student_score GROUP BY studentid
HAVING a = (SELECT COUNT(*) FROM student_course))r WHERE student.id = r.studentid