A.
SELECT COUNT(*) AS 记录数,SUM(cj) as 成绩总和,MAX(cj) AS 最高成绩, MIN(cj) AS 最低成绩,AVG(cj) AS 平均成绩 FROM teachers ;
B.
SELECT COUNT(*) AS 总人数 ,AVG(年龄) AS 平均年龄,MAX(年龄) AS 最大年龄,MIN(年龄) AS 最小年龄 FROM teachers;
C.
SELECT COUNT(*) AS 总人数 ,MAX(年龄) AS 平均年龄,AVG(年龄) AS 最大年龄,MIN(年龄) AS 最小年龄 FROM teachers;
D.
SELECT * FROM teachers GROUP BY 年龄;