A.SELECT COUNT() AS 人数,AVG(YEAR(出生年月)) AS 平均年龄 FROM Students;
B.SELECT COUNT(*) AS 人数,AVG(YEAR(出生年月)) AS 平均年龄 FROM Students;
C.SELECT COUNT(*) AS 人数,AVG(YEAR(DATE())-YEAR(出生年月)) AS 平均年龄 FROM Students;
D.SELECT COUNT() AS 人数,AVG(YEAR(DATE())-YEAR(出生年月)) AS 平均年龄 FROM Students;
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参考答案:C
解析:
【解析】在查询中要统计记录的个数应使用的函数是COUNT(*),COUNT(列名)是返回该列中值的个数;AVG是计算值的平均值,利用当前年份减去出生年份可以求得学生的平均年龄。因此统计学生的人数和平均年龄应使用的语句是SELECT COUNT(*) AS 人数,AVG(YEAR(DATE())-YEAR(出生年月)) AS 平均年龄 FROM Students。