select a.name,b.t_num from table_A a,(select t_id,t_num from table_b where id=81)
)b where a.id=b.t_id

------解决方案--------------------
SQL code

select a.name ,b.t_num  
from table_A a ,table_b b
where a.id = b.t_id 
and b.id=81

------解决方案--------------------
select a.name ,b.t_num 
from table_A a ,table_b b
where a.id = b.t_id  
and b.id=81


------解决方案--------------------
select a.name , b.t_num
from table_a a , table_b b
where a.id = b.t_id and b.id = 81

------解决方案--------------------
SQL code
SELECT 
    a.NAME,b.t_num
FROM table_A AS a
    INNER JOIN table_b AS b ON a.ID=b.t_id
WHERE b.ID=81

------解决方案--------------------
select tt.name,
ss.t_num
from
(select name from table_A t where id in (select t_id from table_b where id=81)) tt,
(select t_num from table_b s where id=81) ss

------解决方案--------------------
SQL code

select A.name, B.t_num  
  from table_A A
  left join table_b B 
  on A.id = B.id
  where  B.id=81