oracle sql如何取回1行只返回結果

Question

我該如何改進這段代碼。

select code,max(total) from 
(select code,count(*) from table_1 group by code) 

上面的代碼，不工作，因爲我試圖從查詢結果集上做MAX函數，但失敗。

Answer 1

如果你只是想號碼，然後你可以使用這個：

select max(total) 
from (
    select code, 
      count(*) as total -- you forgot the column alias here 
    from table_1 
    group by code 
) 

如果你想要的代碼和數，使用以下命令：

with count_result as (
    select code, 
      count(*) as total 
    from table_1 
    group by code 
) 
select code, 
     total 
from count_result 
where total = (select max(total) from count_result);