问题
问答题 简答题
发电厂的汽水损失有哪两大类?
答案
参考答案:
内部损失和外部损失。
发电厂的汽水损失有哪两大类?
参考答案:
内部损失和外部损失。
20~27题使用的数据如表1和表2所示。
表1 教师表(TEACHER.DBF)
|
表2 讲课表(JK.DBF)
|
要求出教师中总学时数前三名的教师的教师号、姓名和总学时数,下列语句中正确的是______。
A.SELECT TOP 3教师号,姓名,总学时数;
FROM TEACHER,JK ORDER BY总学时数
B.SELECT TOP 3 TEACHER.教师号,TEACHER.姓名,SUM(JK.学时)AS总学时;
FROM TEACHER INNER JOIN JK;
WHERE TEACHER.教师号=JK.教师号;
GROUP BY JK.教师号;
ORDER BY 3 DESC
C.SELECT TOP 3 TEACHER.教师号,TEACHER.姓名,SUM(JK.学时)AS总学时;
FROM TEACHER INNER JOIN JK;
ON TEACHER.教师号=JK.教师号;
GROUP BY JK.教师号;
ORDER BY 3 DESC
D.SELECT TOP 3 PERCENT TEACHER.教师号,TEACHER.姓名,;
SUM(JK.学时)AS总学时;
FROM TEACHER INNER JOIN JK;
ON TEACHER.教师号=JK.教师号;
GROUP BY JK.教师号;
ORDER BY 3 DESC