優化查詢數從兩個不同的列總數和一個表的不同行

Question

表佔

Id price  currency  date 
1  10  USD   2013-01-12 
2  200  GBP   2013-01-13 
3  30  GBP   2013-01-14 
4  85  USD   2013-01-20 
5  80  GBP   2013-01-25 
6  120  GBP   2013-01-30 
7  180  GBP   2013-01-31 
8  100  GBP   2013-02-04 

我想就當是從一個月是這樣的：只有

Total: USD  95 
Total: GBP  610 

Answer 1

你需要使用GROUP BY和集合函數SUM()來計算其總數。

SELECT currency, SUM(price) totalPrice 
FROM tableName 
GROUP BY currency 

• SQLFiddle Demo
• SQLFiddle Demo (by month)
• SQLFiddle Demo (by month and year)