下面哪一个语句,显示没有Email地址的教师姓名() A: Select name from teacher where email=NULL; B: Select name from teacher where email C: Select name from teacher where email is NULL; D: Select name from teacher where emailis not NULL;

查询订购单号（字符型，长度为4）尾字符是“l”的错误命令是（ ）。 A: SELECT * FROM 订单 WHERE SUBSTR（订购单号，4）＝’l’ B: SELECT * FROM 订单 WHERE SUBSTR (订购单号，4,1)=’l’ C: SELECT * FROM 订单 WHERE RIGHT(订购单号，1)＝’l’ D: SELECT * FROM 订单 WHERE ‘l’$订购单号

若想查询student表中name为空值的记录，则正确的SQL语句是（1.0分） A: select * from student where name = null; B: select * from student where name link null; C: select * from student where name = 'null'; D: select * from student where name is null;

要从SC表中查找缺成绩（SCORE）的学生学号（NO），相应的SQL语句是（ ）。 A: SELECT NO FROM SC WHERE SCORE = 0 B: SELECT NO FROM SC WHERE SCORE IS 'NULL' C: SELECT NO FROM SC WHERE SCORE = NULL D: SELECT NO FROM SC WHERE SCORE IS NULL

若在教师表中查找还没有输入工龄的记录,使用的SQL语句为 A: SELECT * FROM 教师 WHERE 工龄IS NOT NULL B: SELECT * FROM 教师 WHERE 工龄=0 C: SELECT * FROM 教师 WHERE 工龄 IS NULL D: SELECT * FROM 教师 WHERE 工龄=NULL