如何在子查詢結果上使用MAX（）？

我是Oracle和SQL世界的新手。我有一個問題，我無法弄清楚我的生活，我花了幾個小時嘗試不同的方法，我無法得到我期望的結果。所以繼承我的查詢：如何在子查詢結果上使用MAX（）？

SELECT * 
from(Select membership.mem_desc,membership.mem_max_rentals,membership_history.mem_type,  
    count(membership_history.MEM_TYPE) as membership_count 
    from membership_history 
    JOIN membership ON membership.mem_type = membership_history.mem_type 
    group by (membership_history.mem_type,membership.mem_desc,membership.mem_max_rentals) 
    ) g 
WHERE g.membership_count = (select MAX(membership_count) from g);

因此，內部查詢完美工作，並返回兩個結果。現在我有這兩個值，我想弄清楚如何返回最大的membership_count值，這是我一直在卡住的行。在上面的查詢中，我嘗試在where子句中使用MAX（），但在裏面選擇我不斷收到錯誤'table not found'（意思是'g'）。所以我的問題是如何對我的子查詢的結果使用MAX（）函數？任何想法或建議將不勝感激!!!!!

來源

2013-04-24 user1916441

如果您不知道，[sqlfiddle]（http://www.sqlfiddle.com）確實有Oracle，並且您可以使用各種格式的語句。 – hd1 2013-04-24 03:12:43

你可以嘗試像

SELECT membership.mem_desc,membership.mem_max_rentals,membership_history.mem_type, membership_count, rank() over ORDER BY membership_count DESC as ranky 
from 
(Select membership.mem_desc,membership.mem_max_rentals,membership_history.mem_type,  
count(membership_history.MEM_TYPE) as membership_count 
from membership_history 
JOIN membership ON membership.mem_type = membership_history.mem_type 
group by (membership_history.mem_type,membership.mem_desc,membership.mem_max_rentals) 
) 
WHERE ranky =1;

來源

2013-04-24 03:26:44 Scotch

你並不需要一個發現最大值的子查詢。
相反，你只需要第一行有下令行後：

select * from (
    select 
    membership.mem_desc, 
    membership.mem_max_rentals, 
    membership_history.mem_type,  
    count(membership_history.MEM_TYPE) as membership_count 
    from membership_history 
    JOIN membership ON membership.mem_type = membership_history.mem_type 
    group by (membership_history.mem_type,membership.mem_desc,membership.mem_max_rentals) 
    ORDER BY 4 DESC -- Added this line 
) g 
WHERE ROWNUM = 1. -- Added this line

來源

2013-04-24 05:07:07 Bohemian

您不能直接where子句中使用派生表，它會給table or view does not exist錯誤所以，讓你可以使用HAVING最大計數值條款或Analytical Functions或Rownum等

select * from 
     (Select membership.mem_desc,membership.mem_max_rentals,membership_history.mem_type,  
     count(membership_history.MEM_TYPE) as membership_count 
     from membership_history a 
     JOIN membership b ON b.mem_type = a.mem_type 
     group by (membership_history.mem_type,membership.mem_desc,membership.mem_max_rentals) 
     having count(a.MEM_TYPE) = (Select  
     MAX(count(a.MEM_TYPE)) from membership_history a 
     JOIN membership b ON b.mem_type = a.mem_type 
     group by (a.mem_type,b.mem_desc,b.mem_max_rentals)));

（OR）

select * from 
(SELECT g.*,rank() over (order by membership_count desc) rnk from 
     (Select membership.mem_desc,membership.mem_max_rentals,membership_history.mem_type,  
     count(membership_history.MEM_TYPE) as membership_count 
     from membership_history 
     JOIN membership ON membership.mem_type = membership_history.mem_type 
     group by (membership_history.mem_type,membership.mem_desc,membership.mem_max_rentals)) g) 
WHERE rnk=1;

（OR）

select * from 
(SELECT g.*,rownum rn from 
     (Select membership.mem_desc,membership.mem_max_rentals,membership_history.mem_type,  
     count(membership_history.MEM_TYPE) as membership_count 
     from membership_history 
     JOIN membership ON membership.mem_type = membership_history.mem_type 
     group by (membership_history.mem_type,membership.mem_desc,membership.mem_max_rentals) 
     order by membership_count desc) g) 
WHERE rn=1;

來源

2013-04-24 06:15:04 Aspirant

這是所有好的SQL。

找到一個列值的最佳方式使用最大主鍵列值是：

SELECT .... from tablename 
WHERE ... AND 
    (SELECT max(primary key name) FROM tablename WHERE ....) = primary_key_name

這個例子會返回一個標量值。

來源

2014-04-19 16:48:14 user3552157

我認爲最乾淨的解決方案是使用ALL比較條件。它用於將值與列表或子查詢進行比較。

SELECT 
    m.mem_desc, 
    m.mem_max_rentals, 
    mh.mem_type,  
    COUNT(mh.mem_type) as membership_count 
FROM membership_history mh 
JOIN membership m ON m.mem_type = mh.mem_type 
GROUP BY mh.mem_type,m.mem_desc,m.mem_max_rentals 
HAVING membership_count >= ALL (
    SELECT count(*) 
    FROM membership_history 
    GROUP BY mem_type 
)

來源

2015-06-21 05:12:55 max68

如何在子查詢結果上使用MAX（）？

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