摘要：
存在测试IN、NOT IN、EXISTS、NOT EXISTS例：SELECT * FROM SC WHERE SNO IN(SELECT SNO FROM STUDENT WHERE SSEX=’女’);同：SELECT * FROM SC WHERE EXISTS(SELECT * FROM STUDENT WHERE SSEX=’女’ AND SC.SNO=SNO);返回所有女生的成绩例：SELECT * FROM SC WHERE SNO NOT IN (SELECT SNO FROM STUDENT WHERE SSEX=’女’);同：SELECT * FROM SC WHERE N 阅读全文
