数据库用student表和sc表查询学号只在student表中出现过并且未在sc表中出现采用左连接查询或右连接查询的方式查询学号信息只在student表或只在sc中出现过的记录

左连接查询方式：

SELECT s.* FROM student s LEFT JOIN sc c ON s.sno = c.sno WHERE c.sno IS NULL;

右连接查询方式：

SELECT c.* FROM sc c RIGHT JOIN student s ON c.sno = s.sno WHERE s.sno IS NULL;