mysql - 我可以從同一列中選擇值並將它們顯示在2列結果中嗎？

Question

假設我有一個帳戶項移動表，就像

ACCOUNTS table 
+-------+------+---------+ 
| title | side | balance | 
+-------+------+---------+ 
| cash | debit| 500.0 | 
+-------+------+---------+ 
| cash |credit| 300.0 | 
+-------+------+---------+ 
| cash |credit| 600.0 | 
+-------+------+---------+ 
#..... more than 10'000 debit and credit rows 

我想組信用行之和借記行的總和，並顯示在不同的列他們的每一筆。

什麼，我試圖做的是總結在兩側的羣體的平衡，就像

select title, side, sum(balance) from accounts group by side 

我得到行，一個爲借方金額，另一個是信貸總和，像

+-------+------+---------+ 
| cash | debit| 500.0 | 
+-------+------+---------+ 
| cash |credit| 900.0 | 
+-------+------+---------+ 

---

我想是獲得整個導致一個結果行，德的總和一個字段中的位和另一個字段中的信用總和。我想最終的結果是這樣的

+-------+-------+-------+ 
| cash | 500.0 | 900.0 | 
+-------+-------+-------+ 

謝謝。

Answer 1

您可以使用情況

select title, sum(case side when 'debit' then balance else 0 end), 
    sum(case side when 'credit' then balance else 0 end) 
from accounts 
group by title 

Answer 2

下面是使用子查詢的一個例子。比已經提供的CASE語句冗長得多，但是如果你最終擁有多個標題或者想要進行計算，它就會變得非常簡單。

SELECT 
    title 
    ,credit.credit_balance 
    ,debit.debit_balance 
    ,(credit.credit_balance - debit.debit_balance) AS net 
FROM 
    (SELECT 
     title, 
     sum(balance) debit_balance 
    FROM accounts 
    WHERE 
     side = 'debit' 
    GROUP BY side) debit 
INNER JOIN (
    SELECT 
     title, 
     sum(balance) debit_balance 
    FROM accounts 
    WHERE 
     side = 'credit' 
    GROUP BY side) credit ON debit.title = credit.title 
GROUP BY 
    title;