SQL合計

Question

我有這樣的[MainTable]一個SQLite表：

Date  | Machine | Product | Scrap 
--------------------------------------- 
2012-02-06 | M1  | P1  | 100 
2012-02-06 | M2  | P1  | 110 
2012-02-06 | M2  | P2  | 200 
2012-02-07 | M3  | P3  | 300 

，我希望得到一個查詢，使得這樣的輸出：

Type   | Total   | Scrap 
------------------------------------ 
Machine  | M1   | 100 
Machine  | M2   | 310 
Machine  | M3   | 300 
Product  | P1   | 210 
Product  | P2   | 200 
Product  | P3   | 300 
Date   | 2012-02-06 | 410 
Date   | 2012-02-07 | 300 
Date-Machine | 2012-02-06 M2 | 310 

我問題是，如果我使用UNION ALL來獲取總數，查詢會多次查找[MainTable]。 我想在一次查詢中計算所有總數，以提高使用SQLite查詢而不是java代碼的速度。

我只需要在SQLite中，而不是在另一個引擎上。

Answer 1

與類型，總碎料列創建一個新表，然後插入你需要單獨的SQL語句這樣的數據：

步驟一：創建一個newtable的這些列：（類型，總，廢）

步驟二：運行這些語句：

INSERT INTO newTable 
SELECT "machine" as type, machine, sum(scrap) 
from yourFirstTable; 

INSERT INTO newTable 
SELECT "product" as type, product, sum(scrap) 
from yourFirstTable; 

，或者如果你需要這些都在一個查詢中，你可以做這樣的事情：

SELECT "machine" as type, machine, sum(scrap) 
from yourFirstTable 
UNION 
SELECT "product" as type, product, sum(scrap) 
from yourFirstTable 

等等

您還可以參加多次到同一個表，並得到相同的結果是這樣的：

SELECT TYPE, ITEM, sum(scrap) as sumTot 
FROM (SELECT "machine" as type, machine as item, scrap from yourFirstTable) as A, 
     (SELECT "machine" as type, product as item, scrap) as B 
GROUP BY TYPE, ITEM