A、 SELECT stu_name, COUNT(stu_sex) FROM student GROUP BY stu_sex;
B、 SELECT stu_sex, COUNT(stu_sex) FROM student GROUP BY stu_sex;
C、 SELECT stu_name FROM student GROUP BY stu_sex;
D、 SELECT stu_sex, COUNT(stu_name) FROM student GROUP BY stu_name;
答案：B
A、 SELECT stu_name, COUNT(stu_sex) FROM student GROUP BY stu_sex;
B、 SELECT stu_sex, COUNT(stu_sex) FROM student GROUP BY stu_sex;
C、 SELECT stu_name FROM student GROUP BY stu_sex;
D、 SELECT stu_sex, COUNT(stu_name) FROM student GROUP BY stu_name;
答案：B
A. 执行代码
B. 切换单元格
C. 切换到命令模式
D. 变量补全
A. var a = 2
B. int a = 2
C. a = 2
D. variable a = 2
A. 5
B. 3
C. 7
D. 9
解析：相关系数的取值在[-1,1]上，-1表示负相关，即变换相反，1表示正相关，0则表示不相关。
A. 0
B. 1
C. 3.1416
D. 2.7183
A. select * from teacher where tage between 30 and 40
B. select * from teacher where tage >= 30 and tage <= 40
C. select * from teacher where tage in (＇30＇,＇40＇)
D. select * form teacher where tage > 30 and tage < 40
