oracle查询sql练习技巧（这个很实用，不是吹的）

--------------使用decode函数
select b.menu_id,decode(b.is_tree,'1','1vv','2','2vv',null,'isnullvalue','defaultvaluehehe') tree
from menutree b

--------------使用case when then else达到相同效果
select c.menu_id,
case
when c.is_tree is null then 'isnullvalue'
when c.is_tree='1' then '1vv'
when c.is_tree='2' then '2vv'
else 'defaultvaluehehe'
end tree
from menutree c