query the student numbers of students who have not taken all courses
idea: students whose counting items are less than the course number mean that they have not learned all the courses
< table > < thead > < tr > < th > s_id < / th > < th > c_id < / th > < th > s_mark < / th > < / tr > < / thead > < tbody > < tr > < td > 01 < / td > < td > 01 < / td > < td > 80 < / td > < / tr > < tr > < td > 01 < / td > < td > 02 < / td > < td > 90 < / td > < / tr > < tr > < td > 01 < / td > < td > 03 < / td > < td > 99 < / td > < / tr > < tr > < td > 02 < / td > < td > 01 < / td > < td > 70 < / td > < / tr > < tr > < td > 02 < / td > < td > 02 < / td > < td > 60 < / td > < / tr > < tr > < td > 02 < / td > < td > 03 < / td > < td > 80 < / td > < / tr > < tr > < td > 03 < / td > < td > 01 < / td > < td > 80 < / td > < / tr > < tr > < td > 03 < / td > < td > 02 < / td > < td > 80 < / td > < / tr > < tr > < td > 03 < / td > < td > 03 < / td > < td > 80 < / td > < / tr > < tr > < td > 04 < / td > < td > 01 < / td > < td > 50 < / td > < / tr > < tr > < td > 04 < / td > < td > 02 < / td > < td > 30 < / td > < / tr > < tr > < td > 04 < / td > < td > 03 < / td > < td > 20 < / td > < / tr > < tr > < td > 05 < / td > < td > 01 < / td > < td > 76 < / td > < / tr > < tr > < td > 05 < / td > < td > 02 < / td > < td > 87 < / td > < / tr > < tr > < td > 06 < / td > < td > 01 < / td > < td > 31 < / td > < / tr > < tr > < td > 06 < / td > < td > 03 < / td > < td > 34 < / td > < / tr > < tr > < td > 07 < / td > < td > 02 < / td > < td > 89 < / td > < / tr > < tr > < td > 07 < / td > < td > 03 < / td > < td > 98 < / td > < / tr > < / tbody > < / table > s_id student number, c_id course number
query sentence is as follows:
select b.s_id from school.mark b where (count (b.s_id) group by b.s_id) < count (distinct b.c_id);
syntax error, do not know how to change