比较两个表的数据关系

Question

我的SQL查询是：

UPDATE REGISTRUDENT set qual=1  
                WHERE studentolevelsubjects AS sls
                INNER JOIN courserequirements AS csreq ON sls.subject_id = csreq.subject_id
                WHERE sls.stud_id = '$stud_id' AND sls.grade_id>=csreq.min_grade AND sls.examno = '$examno' AND csreq.course_id = '$course_id'

如果注册人根据我需要帮助的课程要求获得资格，我有问题比较两个不同的表

课程要求表

学生在考试中通过了该科目

如果学生符合条件，我打算更新并设置qual = 1

非常感谢

Answer 1

您的查询语法不正确。它应该是

UPDATE REGISTRUDENT rs   
JOIN studentolevelsubjects sls ON sls.some_column = rs.some_column //missing this JOIN
JOIN courserequirements csreq ON sls.subject_id = csreq.subject_id
AND sls.grade_id >= csreq.min_grade 
WHERE sls.stud_id = '$stud_id'  
AND sls.examno = '$examno' 
AND csreq.course_id = '$course_id'
SET rs.qual = 1;