01 02040509年
我正在尝试制作一个表格,显示哪些教师正在教授他们没有资格教授的课程。
我有两个数据表:
认证
subject_cert我想你是在找
SELECT
t.instructor,
t.subject_taught,
c.subject_cert
FROM taught_course AS t
LEFT JOIN certification AS c
ON t.instructor = c.instructor_id AND t.subject_taught = c.subject_cert
WHERE c.instructor_id IS NULL
ORDER BY
t.instructor,
t.subject_taught,
c.subject_cert ASC;
这是您的查询,但是我添加了第二个条件(AND t.subject_taught = c.subject_cert
)到连接,因为您想要匹配主题以及教师,我添加了WHERE c.instructor_id IS NULL
,因为您只想返回左连接未能找到匹配的行。