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CREATE VIEW tea_view(avg_grade)
AS
SELECT avg(a.grade)
FROM stud_grade a,lesson_info b
GROUP BY a.course_id
HAVING a.course_id=(select course_id from lesson_info where course_name='计算机导论')
列 'a.NAME' 在选择列表中无效,因为该列既不包含在聚合函数中,也不包含在 GROUP BY 子句中。
CREATE VIEW tea_view(stuid,name,avg_grade)
AS
SELECT stud_id,name,
(SELECT avg(a.grade)
FROM stud_grade a,lesson_info b
GROUP BY a.course_id
HAVING a.course_id=(select course_id from lesson_info where course_name='计算机导论'))
FROM stud_info
WHERE substring(stud_id,3,2)='01'
CREATE VIEW tea_view
AS
SELECT a.id,a.name,b.avg_grade
FROM stud_grade a,
(select course_id,avg(a.grade) as avg_grade from lesson_info
where course_name='计算机导论'
group by course_id
) b
where a.course_id=b.course_id
CREATE VIEW tea_view(avg_grade)
AS
SELECT
a.course_id,avg(a.grade)
FROM
stud_grade a,lesson_info b
GROUP BY
a.course_id
HAVING
a.course_id=(select course_id from lesson_info where course_name='计算机导论')
CREATE VIEW tea_view
AS
SELECT a.id,a.name,avg(a.grade) as avg_grade
FROM stud_grade a,lesson_info b
where a.course_id=b.course_id
and b.course_name='计算机导论'
GROUP BY a.id,a.name