下列选项中哪一个是正确的空值查询条件的SQL表达（）
A. ＜ ＞NULL
B. !=NULL
C. IS NOT NULL
D. NOT IS NULL
查看答案
检索选修了课程”C1”的学生中成绩最高的学生的学号，正确的SELECT语句为（）
A. SELECT Sno FROM SC WHERE Cno=’C1’ AND GRADE ＞=ALL （SELECT Grade FROM SC WHERE Cno=’C1’）
B. SELECT Sno FROM SC WHERE Cno=’C1’ AND GRADE IN （SELECT Grade FROM SC WHERE Cno=’C1’）
C. SELECT Sno FROM SC WHERE Cno=’C1’ AND GRADE ＞ ANY （SELECT Grade FROM SC WHERE Cno=’C1’）
D. SELECT Sno FROM SC WHERE Cno=’C1’ AND GRADE ＞= （SELECT Grade FROM SC WHERE Cno=’C1’）
After using reagents in chemical lab, you should to（）
A. put it back in place immediatel
B. put it in an easy accessing place
C. make up by yourself,when it is insufficient
D. keep the bottle open for easy use next time
列出SC表中所有考试不及格的学生的学号Sno（无须重复），其SQL语句为（）
A. SELECT DISTINCT Sno FROM SC WHERE Grade＜60;
B. SELECT DISTINCT Sno FROM SC WHERE Grade IS NULL;
C. SELECT Sno FROM SC WHERE Grade＜60;
D. SELECT ALL Sno FROM SC WHERE Grade＜60;
Do not wear（）in inflammable and explosive places
A. Cloth shoes
B. Rubber shoes
C. Spiked shoes
D. Sneakers
微信支付 
支付宝支付