案例十一:查询学生表的学号,姓名和所在年级
SELECT studentno AS '学号',studentname AS '姓名',gradename AS '年级' FROM student AS s LEFT JOIN grade AS g ON s.gradeid= g.gradeid;
SELECT studentno AS '学号',studentname AS '姓名',gradename AS '年级' FROM student AS s LEFT JOIN grade AS g ON s.gradeid= g.gradeid;