sql语句搜索唯一字段

sql语句搜索唯一字段

例子：
有一个表　Table1,有两个字段 ACCOUNT_ID CATEGORY_ID.

ACCOUNT_ID  CATEGORY_NAME
    1            a
    2            b
    3            a
    1            c
    2            c
    4            a
    1            e

a对应1.3.4 , c对应1.2.
b只对应2， e只对应1。

问题：我想查找 CATEGORY_NAME所对应的ACCOUNT_ID只有一个种类的。就像b只对应2，e只对应1。
就是想找b和e 怎么找？？？？
用selece from where 怎么实现

select CATEGORY_NAME
from table1
group by CATEGORY_NAME
having count(distinct ACCOUNT_ID)=1 
 

SQL codeselect *
from Table1 a
where not exists(
    select 1 from Table1
    where CATEGORY_NAME=a.CATEGORY_NAME
    and ACCOUNT_ID!=a.ACCOUNT_ID)

select account_id,CATEGORY_NAME from temp where CATEGORY_NAME in(
select CATEGORY_NAME from(
select account_id,CATEGORY_NAME from temp group by account_id,CATEGORY_NAME
) group by CATEGORY_NAME having count(CATEGORY_NAME) = 1
)group by account_id,CATEGORY_NAME