问题SQL语法

Question

的SQL语法如下：

SELECT y.NAME, y.EMAIL, k.DATE, k.WORK_NR, k.SCORE, k.FILENAME 
FROM bas1.students y, bas1.assignments k, bas1.topics a 
WHERE y.ID = k.student_id AND k.topic_id = a.id 
WHERE a.NAME = 'History'; 

，但我得到了一些错误，任何想法？

Answer 1

您使用WHERE两次

SELECT y.NAME, y.EMAIL, k.DATE, k.WORK_NR, k.SCORE, k.FILENAME 
FROM bas1.students y, bas1.assignments k, bas1.topics a 
WHERE y.ID = k.student_id AND k.topic_id = a.id 
AND a.NAME = 'History'; 

改变这种

Answer 2

你不需要加入语句？例如，

SELECT y.NAME, y.EMAIL, k.DATE, k.WORK_NR, k.SCORE, k.FILENAME 
FROM bas1.students y JOIN bas1.assignments k ON y.ID = k.student_id 
JOIN bas1.topics a ON k.topic_id = a.id 
WHERE a.NAME = 'History';