--22. 查询选修课程成绩至少有一门在80分以上的学生学号: select distinct sno from sc where grade>80 go --23. 查询选修课程成绩均在80分以上的学生学号: select distinct sno from sc where 80<(select min(grade) from sc y where y.sno=x.sno ) go --24. 查询选修课程平均成绩在80分以上的学生学号: select sno from sc group…
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原文:SQL点滴12-SQL Server备份还原数据库中的小把戏 备份数据库时出现一个不太了解的错误 ,错误信息“is formatted to support 1 media families, but 2 media families are expected according to the backup device specification”.如下图: 解决办法是首先选中击上一次备份的文件,点击Remove,去掉当前的备份文件,然后再点击OK备份.这样才能正确的备份.也在微软帮助…