SQL如何分类组合查询?
现有表
course,列为course_uid,course_name
enrolled,列为course_uid,student_uid
现在想将每个COURSE_UID分别由STUDENT_UID数列出来,同时列出相应COURSE_UID对应的COURSE_NAME值
我尝试写成
- SQL code
SELECT Course_Name, ( SELECT count( * ) FROM `enrolled` GROUP BY Course_Uid ) FROM course WHERE Course_Uid IN ( SELECT Course_Uid FROM enrolled GROUP BY Course_Uid );
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但无法得到想要的值,SQL提示Subquery returns more than 1 row
——解决方案——————–
- SQL code
select a.course_uid,a.course_name,count(b.student_uid) cout from course a,enrolled b where a.course_uid=b.course_uid group by a.course_uid;