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 

select   grade, count (case when *** = 1 then 1 /**** 1為男生，2位女生*/

else null
end) 男生數,
count (case when *** = 2 then 1
else 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 1
when t2.compare_type != 'a' and
t1.some_type not like 'nothing%'
then 1
else 0
end) = 1

select  

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