Question

我正在尝试计算用户获得的所有正确答案，并在分数表中更新它。但它给了我一个有趣的小错误。

UPDATE score
SET end_time = CURTIME(), final_score = COUNT(
    SELECT *
    FROM answered
    WHERE (exam_id = 8 and student_login = 'user' and guessed = 1)
)
WHERE exam_id = 8 and student_login = 'user'

错误：

＃1064 - 您的SQL语法出错;检查手册对应于您的MySQL服务器版本，以便使用正确的语法 'SELECT * FROM answers WHERE附近（exam_id = 8和student_login = 'user'和gue'在第3行

这应该够简单吧？那么这个错误到底是什么？选择单独工作。并且更新在没有final_score更新的情况下工作。

感谢您的帮助！

Answer 1

UPDATE score
SET end_time = CURTIME(), final_score = (
    SELECT COUNT(*)
    FROM answered
    WHERE (exam_id = 8 and student_login = 'user' and guessed = 1)
)
WHERE exam_id = 8 and student_login = 'user'

应该这样做。

COUNT不能（据我所知）对子查询进行操作。

Answer 2

试试这个：

UPDATE score
SET end_time = CURTIME(), final_score = (
    SELECT COUNT(*)
    FROM answered
    WHERE (exam_id = 8 and student_login = 'user' and guessed = 1)
)
WHERE exam_id = 8 and student_login = 'user'

Answer 3

试试这个..

UPDATE score
SET end_time = CURTIME(), final_score = (
    SELECT cnt=count(*)
    FROM answered
    WHERE (exam_id = 8 and student_login = 'user' and guessed = 1)
)
WHERE exam_id = 8 and student_login = 'user'

从子查询的计数中更新值

3 个答案: