根据我国煤矿现阶段的防尘技术条件和技术装备,矿井综合防尘措施可大致归纳为五大类()。
A.减尘
B.降尘
C.捕尘
D.排尘
E.阻尘
参考答案:A, B, C, D, E
每千克香蕉a元,每千克苹果的价钱是香蕉的2倍少0.5元,每千克苹果的价格是______元.
设有关系模式:student(sno,sname,age,dept),现利用命令: CREATE VIEW stu AS SELECT*FROM student WHERE dept="CS"WITH CHECK OPTION 创建了一个视图。则下TSQL命令巾能正确执行的是()
A. UPDATE stu SET dept="maths"
B. UPDATE stu SET dept="maths" WHERE age>=20
C. INSERT INTO stu VALUES("2004001","John",30,"cs")
D. INSFRT INTO stu VALUES("2004001","John",50,"maths")