单项选择题
A.select to_char(sysdate,'D') from dual; B.select to_char(sysdate,'W') from dual; C.select to_char(sysdate,'D')-1 from dual; D.select to_char(sysdate-1,'D') from dual; E.select to_char(sysdate-1,'W') from dual;
A.select * from emp where hiredate>='19820101'; B.select * from emp where hiredate>=to_char('19820101','YYYYMMDD'); C.select * from emp where to_date(hiredate,'YYYYMMDD')>='19820101'; D.select * from emp where to_char(hiredate,'YYYYMMDD')>='19820101';
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;