MySQL MAX與第二列相關

Question

我試圖獲得與一個國家的賬戶相關的最長和最短的1年時間。這些數據是從一個表中提取的。

對於一個國家，我將擁有帳戶一的最高帳戶回報和帳戶二的最低帳戶回報。所以每個國家1個結果。

我有以下但它不能正常工作，它實際上爲我提供了來自不正確帳戶的最高和最低值，因爲它應該只與擁有1年時間範圍的帳戶一起工作。

也忘了補充說明dpromo_one的總體結果，只對這些國家例如（'美國'，'英國'，'南非'，'印度'，'澳大利亞'）只要。它剛剛變得非常複雜，它讓我頭腦發熱。

SELECT DISTINCT acc2.account_name AS account_one, acc5.account_name AS account_two, 
    MAX(acc2.dpromo_rate) AS dpromo_one, MIN(acc5.dpromo_rate) AS dpromo_two, 
    acc2.deposit_term, acc2.country 
FROM accounts acc2 
INNER JOIN accounts acc5 ON acc2.country = acc5.country 
WHERE acc2.type =2 
AND acc5.type =2 
AND acc2.deposit_term = '1 Year' 
GROUP BY country 

整體輸出例如可能是1號線以下 ：

Country Bank Highest Bank    Lowest 
USA  BOFA 1yr  1%  Wells Fargo 1yr 0.5% 
UK  HSBC 1yr  0.5% Halifax 1yr  0.25% 
Australia CBA 1yr  0.4% NAB 1yr   0.1% 

例如賬表有例如是相關

ACCOUNT_NAME 國家 dpromo_rate deposit_term以下字段

請注意，我們一個重新擁有帳戶和價格並排。我的代碼這樣做，但不正確，雖然這就是爲什麼它也解釋了爲什麼我有別名重複的字段名稱。

Answer 1

它正在做究竟是 MySQL說它會做什麼。 group by子句中未包含的列具有任意值。在大多數其他數據庫中，查詢只會因語法錯誤而失敗。

這裏有個竅門，以獲得帳戶的名稱：

SELECT substring_index(group_concat(acc2.account_name order by acc2.dpromo_rate desc), ',', 1) AS account_one, 
     substring_index(group_concat(acc5.account_name order by acc5.dpromo_rate asc), ',', 1) AS account_two, 
     MAX(acc2.dpromo_rate) AS dpromo_one, MIN(acc5.dpromo_rate) AS dpromo_two, 
     acc2.deposit_term, acc2.country 
FROM accounts acc2 
INNER JOIN accounts acc5 ON acc2.country = acc5.country 
WHERE acc2.type =2 AND acc5.type =2 AND acc2.deposit_term = '1 Year' 
GROUP BY country 

我認爲你可以簡化查詢到一個簡單的聚集。我不明白爲什麼你在做一個連接：

SELECT substring_index(group_concat(acc.account_name order by acc.dpromo_rate desc), ',', 1) AS account_one, 
     substring_index(group_concat(acc.account_name order by acc.dpromo_rate asc), ',', 1) AS account_two, 
     MAX(acc.dpromo_rate) AS dpromo_one, MIN(acc.dpromo_rate) AS dpromo_two, 
     acc.deposit_term, acc.country 
FROM accounts acc 
WHERE acc.type = 2 and acc.deposit_term = '1 Year' 
GROUP BY country; 

如果您打算在存款期限只適用於max，然後替換爲最大：

max(case when acc.deposit_term = '1 Year' then acc.dpromo_rate end) as dpromo_one 

Answer 2

我的事情這將給結果

select max(dpromo_rate), min(dpromo_rate), country, account_name, provider from accounts 
where deposit_term = '1 Year' group by country, provider, account_name 

Answer 3

爲了讓你的基礎在輸出例如： -

SELECT DISTINCT z.county, b.account_name, b.dpromo_rate, d.account_name, d.dpromo_rate 
FROM accounts z 
INNER JOIN (SELECT country, type, MAX(dpromo_rate) AS MaxRate FROM accounts WHERE type = 2 AND deposit_term = '1 Year' GROUP BY country, type) a 
ON z.country = a.country AND z.type = a.type 
INNER JOIN accounts b 
ON a.country = b.country and a.MaxRate = b.dpromo_rate AND a.type = b.type 
INNER JOIN (SELECT country, type, MIN(dpromo_rate) AS MinRate FROM accounts WHERE type = 2 AND deposit_term = '1 Year' GROUP BY country, type) c 
ON z.country = c.country AND z.type = c.type 
INNER JOIN accounts d 
ON c.country = d.country and c.MinRate = d.dpromo_rate AND c.type = d.type 

這只是獲取國家，帳戶名稱與最大利率，實際最高利率，帳戶名稱與最低利率和實際最低利率。

不確定在輸出中需要存款期限和提供者，但它們很容易從b或d別名表中獲得。

請注意，如果您在一個國家擁有多個帳戶，並且所有帳戶都分享最高或最低費率，這會造成混亂。

要限制它的最大速度的幾個國家和秩序： -

SELECT DISTINCT z.county, b.account_name, b.dpromo_rate, d.account_name, d.dpromo_rate 
FROM accounts z 
INNER JOIN (SELECT country, type, MAX(dpromo_rate) AS MaxRate FROM accounts WHERE type = 2 AND deposit_term = '1 Year' GROUP BY country, type) a 
ON z.country = a.country AND z.type = a.type 
INNER JOIN accounts b 
ON a.country = b.country and a.MaxRate = b.dpromo_rate AND a.type = b.type 
INNER JOIN (SELECT country, type, MIN(dpromo_rate) AS MinRate FROM accounts WHERE type = 2 AND deposit_term = '1 Year' GROUP BY country, type) c 
ON z.country = c.country AND z.type = c.type 
INNER JOIN accounts d 
ON c.country = d.country and c.MinRate = d.dpromo_rate AND c.type = d.type 
WHERE z.country IN ('united states', 'united kingdom', 'south africa', 'india', 'australia') 
ORDER BY b.dpromo_rate 

將其限制在每個國家之一，那麼你可以這樣做： -

SELECT z.county, b.account_name, b.dpromo_rate, d.account_name, d.dpromo_rate 
FROM accounts z 
INNER JOIN (SELECT country, type, MAX(dpromo_rate) AS MaxRate FROM accounts WHERE type = 2 AND deposit_term = '1 Year' GROUP BY country, type) a 
ON z.country = a.country AND z.type = a.type 
INNER JOIN accounts b 
ON a.country = b.country and a.MaxRate = b.dpromo_rate AND a.type = b.type 
INNER JOIN (SELECT country, type, MIN(dpromo_rate) AS MinRate FROM accounts WHERE type = 2 AND deposit_term = '1 Year' GROUP BY country, type) c 
ON z.country = c.country AND z.type = c.type 
INNER JOIN accounts d 
ON c.country = d.country and c.MinRate = d.dpromo_rate AND c.type = d.type 
WHERE z.country IN ('united states', 'united kingdom', 'south africa', 'india', 'australia') 
GROUP BY z.county 
ORDER BY b.dpromo_rate 

注意，如果一個國家的2個賬戶具有相同的匯率，這是該國家的最高匯率，那麼只有一個賬戶可以退貨。哪一個返回是不確定的。