将student表按照gender字段进行分组查询，查询出grade字段值之和小于300的分组，依据上述要求，下面选项中，正确的SQL语句是（）
A. SELECT sum(grade),gender FROM student GROUP BY gender HAVING SUM(grade)<300;
B. SELECT sum(grade),gender FROM student GROUP BY gender WHERE SUM(grade)<300;
C. SELECT sum(grade),gender FROM student WHERE SUM(grade)<300 GROUP BY gender;
D. 以上语句都不对
查看答案
进行子查询时，用于测试条件返回的是TRUE或FALSE的关键字是（ ）
A. IN
B. ON
C. EXISTS
D. NOT IN
给定如下SQL语句：SELECT employee.name, department.dname FROM department,employeeWHERE department.did=employee.did;下面选项中，与其功能相同的是（ ）
A. SELECT employee.name, department.dname FROM department JOIN employee ON department.did=employee.did;
B. SELECT employee.name, department.dname FROM department CROSS JOIN employee ON department.did=employee.did;
C. SELECT employee.name, department.dname FROM department LEFT JOIN employee ON department.did=employee.did;
D. SELECT employee.name, department.dname FROM department RIGHT JOIN employee ON department.did=employee.did;
下面选项中，在SELECT语句中用于代表所有字段的通配符是（ ）
A. *
B. ?
C. +
D. %
下面关于交叉连接本质的说法中，正确的是（ ）
A. 两表进行内连接
B. 两表进行左外连接
C. 两表进行右外连接
D. 两表进行笛卡尔积
微信支付 
支付宝支付