[英]Unknown Column in Where Clause : Mysql Update Query
This is my update query:这是我的更新查询:
update grade
set grade='A'
where (select assignment*0.3+midExam*0.35+finalExam*0.35 as FINALSCORE
from taking) >= 85
and taking.student_id = grade.student_id
and taking.subject_id = grade.subject-id;
and the result is below结果如下
Unknown column 'taking.student_id' in 'where clause'
'where 子句'中的未知列'taking.student_id'
What am i doing wrong?我究竟做错了什么?
The table taking
is inside a subquery then is not visible outside the subquery taking
表在子查询内,然后在子查询外不可见
for your need you should use an update with join根据您的需要,您应该使用带有连接的更新
update grade
INNER JOIN taking ON taking.student_id=grade.student_id
and taking.subject_id=grade.subject_id
and taking.assignment*0.3+taking.midExam*0.35+taking.finalExam*0.35 >= 85
set grade='A'
for a general solution通用解决方案
you could try adding a case when for each grade您可以尝试为每个年级添加一个案例
update grade
INNER JOIN taking ON taking.student_id=grade.student_id
and taking.subject_id=grade.subject_id
set grade = (case when taking.assignment*0.3+taking.midExam*0.35+taking.finalExam*0.35 >= 85 THEN 'A'
when taking.assignment*0.3+taking.midExam*0.35+taking.finalExam*0.35 between 60.0 and 84.9 THEN 'B'
ELSE 'C' END)
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