The second question, for example, he has to query the proportion of boys and girls in grades of students, but this information is not a table top, this how to query for bosses to give directions

CodePudding user response:

Join the or apply

CodePudding user response:

The select Arthur c. no, count (s.s no), sum (s.s core) from course c
Left the join sc s on Arthur c. no=s.c no group by Arthur c. no