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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