子查询
-- ===================== where ============================= -- 1、查询数据库结构-1的所有考试结果(学号,科目编号,成绩),降序排列 -- 方式一:使用连接查询 SELECT r.`studentno`,r.`subjectno`,`studentresult` FROM result r INNER JOIN `subject` sub ON r.`subjectno` = sub.`subjectno` WHERE `subjectname`='数据库结构-1' ORDER BY studentResult DESC -- 方式二:使用子查询(由里及外) -- 查询所有数据库结构-1的学生学号 SELECT r.`studentno`,r.`subjectno`,`studentresult` FROM result r WHERE subjectno =( SELECT subjectno FROM `subject` WHERE `subjectname`='数据库结构-1' ) -- 查询课程为高等数学-2 且 分数不小于80分学生的学号和姓名 SELECT s.`studentno`,`studentname` FROM `student` s INNER JOIN `result` r ON s.`studentno` = r.`studentno` INNER JOIN `subject` sub ON r.`subjectno` = sub.`subjectno` WHERE sub.`subjectname` = '高等数学-2' AND `studentresult`>=80 -- 分数不小于80分的学生的学号和姓名 SELECT DISTINCT s.`studentno`,`studentname` FROM student s INNER JOIN result r ON s.`studentno`=r.`studentno` WHERE `studentresult`>=80 -- 在这个基础上增加一个科目,高等数学-2 -- 查询高等数学-2 的编号 SELECT DISTINCT s.`studentno`,`studentname` FROM student s INNER JOIN result r ON s.`studentno`=r.`studentno` WHERE `studentresult`>=80 AND `subjectno` = (SELECT `subjectno` FROM `subject` WHERE `subjectname`='高等数学-2') -- 再改造(由里及外) SELECT `studentno`,`studentname` FROM `student` WHERE `studentno`=( SELECT `studentno` FROM `result` WHERE `studentresult`>=80 AND `subjectno`=( SELECT `subjectno` FROM `subject` WHERE `subjectname`='高等数学-2' ) )
标签:--,查询,studentno,subjectno,result,WHERE,SELECT From: https://www.cnblogs.com/1982king/p/16610564.html