在Oracle中,下面哪条语句当COMM字段为空时显示0,不为空时显示COMM的值()。
A、select ename,nvl(comm.,0)from emp
B、select ename,null(comm.,0)from emp
C、SELECT ename,NULLIF(comm,0)FROM emp
D、SELECT ename,DECODE(comm.,NULL,0)FROM emp
A、select ename,nvl(comm.,0)from emp
B、select ename,null(comm.,0)from emp
C、SELECT ename,NULLIF(comm,0)FROM emp
D、SELECT ename,DECODE(comm.,NULL,0)FROM emp
A、A.CREATE PUBLIC SYNONYM cust ON mary.customer B、B.CREATE PUBLIC SYNONYM cust FOR mary.customer C、C.CREATE SYNONYM cust ON mary.customer FOR PUBLIC D、D.不能创建CUSTOMER的公用同义词
A、使用set statistics io语句 B、使用set statistics time语句 C、使用set statistics CPU语句 D、使用set statistics time and CPU语句