sql语法的问题

Question

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';

但我得到一些错误，任何想法？

Answer 1

你正在使用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';

更改为

Answer 2

你不需要加入声明吗？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';