每天10句SQL（1）

1. select max(grade) as 最高成绩 ,min(grade)as 最低成绩 from student_course where grade<90 ----------------------------------------------------------------------------------- 2. select sum(grade) from student_course ----------------------------------------------------------------------------------- 3. select count(*),count(student_id) from student ----------------------------------------------------------------------------------- 4. select * from student_course where grade>60 order by grade desc ----------------------------------------------------------------------------------- 5. select * from student_course where grade in('90' ,'98') ----------------------------------------------------------------------------------- 6. select * from student_course where grade >60 and grade<80 order by grade asc ----------------------------------------------------------------------------------- select * from student_course where grade between 60 and 80 order by grade asc ----------------------------------------------------------------------------------- select * from student_course where (grade between 60 and 80) or (grade between 20 and 40) order by grade asc ----------------------------------------------------------------------------------- 7. select grade, count(*) from student_course where grade>60 group by grade ----------------------------------------------------------------------------------- 8. select grade, count(*) from student_course group by grade having count(*)>1 ----------------------------------------------------------------------------------- select grade, count(*) from student_course group by grade having count(*)=1 or count(*)=3 ----------------------------------------------------------------------------------- select grade, count(*) from student_course group by grade having count(*) in('1','3') ----------------------------------------------------------------------------------- 9. select top 5 * from student_course ----------------------------------------------------------------------------------- select top 3 * from student_course where student_id not in ( select top 3 student_id from student_course order by grade desc ) order by grade desc ----------------------------------------------------------------------------------- 10. select course_id from student_course ----------------------------------------------------------------------------------- select distinct course_id from student_course ----------------------------------------------------------------------------------- select distinct course_id ,student_id from student_course