此查询：

select id_b
from tablename
group by id_b
having count(*) = 1

返回所有 id_b 你想要的，所以和接线员一起使用 IN :

select * 
from tablename
where id_b in (
  select id_b
  from tablename
  group by id_b
  having count(*) = 1
)

这可能更简单，假设您有一个主键。然后你可以加上“和t2.id\u b=…”

SELECT t1.*
FROM tablename as t1
  LEFT JOIN tablename as t2 
      ON t1.id_b = t2.id_b AND t1.primarykey <> t2.primarykey
WHERE t2.primarykey IS NULL

或以下语法：

SELECT t1.*
FROM tablename as t1
WHERE NOT EXISTS (SELECT 'x'
                  FROM tablename as t2 
                  WHERE t1.id_b = t2.id_b AND t1.primarykey <> t2.primarykey)

如果需要行，请使用窗口函数：

select t.*
from (select t.*, count(*) over (partition by b) as cnt_b
      from t
     ) t
where t2.id_b = ? and cnt_b = 1;

如果你只是想 b 值，使用聚合：

select b
from t
group b
having min(b) = max(b) and min(b) = ?;