单项选择题
查询出EMP表中COMM字段为空的记录（）
A.select * from emp where comm='';
B.select * from emp where comm=null;
C.select * from emp where nvl(comm)=0;
D.select * from emp where comm is null;
E.select * from emp where nvl(comm,0)=0;
相关考题
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单项选择题
取出工资在2000到3000元（包括上下限）之间的员工（）
A.select * from emp wher sal in (2000,3000);
B.select * from emp wher sal like (2000,3000);
C.select * from emp wher sal = (2000,3000);
D.select * from emp wher sal between 2000 and 3000; -
单项选择题
查询出所有名字以’S’开始的员工（）
A.select * from emp where ename in 'S%';
B.select * from emp where ename='S%';
C.select * from emp where ename like 'S%';
D.select * from emp where ename like 'S_'; -
单项选择题
查询出当前的数据库系统时间，精确到秒（）
A.select to_date(sysdate,'YYYY-MM-DD HH24:MI:SS') from dual;
B.select to_char(sysdate,'YYYY-MM-DD HH24:MI:SS') from dual;
C.select date(sysdate,'YYYY-MM-DD HH24:MI:SS') from dual;
D.select chr(sysdate,'YYYY-MM-DD HH24:MI:SS') from dual;
