orcale学习-常用函数

to_char(sysdate,'yyyy-mm-dd hh:mi:ss') from dual
to_date
to_number
nvl(common,0) --将把空替换为0
nvl2(exp1,expr2,expr3)   --expr==expr2?null:epxr1

case语句

select ename,job,sal,
    case job when 'SALESMAN'  then sal*0.9
            when 'MANAGER' then sal*0.85
from salary 

decode函数

select ename,job,sal,
    decode(job,'SALESMAN',sal*0.9,
                'MANAGER',sal*0.85
          )as t_sal  --别名
from semp