4.转换函数:

---to_char
select to_char(hiredate,'yyyy-mm-dd') from emp
select to_char (hiredate,'yyyy"年"mm"月"dd"日"') from emp@H_301_11@ 
 
select sal,to_char (sal,'l0,000,000.00') as saltest from emp@H_301_11@ 
结果:
 
 
查询入职时间在1982年之后的员工:
select ename,hiredate from emp where hiredate>to_date('1981-12-31','yyyy-mm-dd')@H_301_11@ 
 
查询工资大于2000的所有员工:
select ename,sal from emp where sal>to_number('¥2000','l9999');@H_301_11@ 
5.通用函数: