Oracle CASE WHEN 用法介紹

源：

評：

--

簡單case函式  
case ***  
when'1
'then'男
'when'2
'then'女
'else'其他
'end
--case搜尋函式  
case
when *** ='1
'then'男
'when *** ='2
'then'女
'else'其他
'end

select   grade, count (case

when *** =
1then1/*
*** 1為男生，2位女生
*/else
null
end) 男生數,
count (case
when *** =
2then
1else
null
end) 女生數
from students group
by grade;

select t2.*, t1.*

from t1, t2
where (case
when t2.compare_type ='a
'and
t1.some_type like
'nothing%
'then
1when t2.compare_type !='a
'and
t1.some_type not
like
'nothing%
'then
1else
0end) =
1

select

case
when salary <=
500then'1
'when salary >
500and salary <=
600then'2
'when salary >
600and salary <=
800then'3
'when salary >
800and salary <=
1000
then'4
'else
null
end salary_class, --
別名命名
count(*)  
from    table_a  
group
bycase
when salary <=
500then'1
'when salary >
500and salary <=
600then'2
'when salary >
600and salary <=
800then'3
'when salary >
800and salary <=
1000
then'4
'else
null
end;

select decode(***, '

m', '
male
', '
f', '
female
', '
unknown
')from   employees;

3.2 在where中特殊實現

select t2.*, t1.*

from t1, t2
where (t2.compare_type ='a
'and t1.some_type like
'nothing%
')         or
(t2.compare_type !='a
'and t1.some_type not
like
'nothing%
')

Oracle CASE WHEN 用法介紹

簡單case函式 case when 1 then 男 when 2 then 女 else 其他 end case搜尋函式 case when 1 then 男 when 2 then 女 else 其他 end 2.1 select case when 用法 select grade,count...

Oracle CASE WHEN 用法介紹

簡單case函式 case when 1 then 男 when 2 then 女 else 其他 end case搜尋函式 case when 1 then 男 when 2 then 女 else 其他 end 2.1 select case when 用法 select grade,count...

Oracle CASE WHEN 用法介紹

簡單case函式 case when 1 then 男 when 2 then 女 else 其他 end case搜尋函式 case when 1 then 男 when 2 then 女 else 其他 end 2.1 select case when 用法 select grade,count...