Question

我有一个类似[MainTable]的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

我希望得到一个像这样输出的查询：

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

我的问题是，如果我使用UNION ALL来获取总数，那么查询会多次查找[MainTable]。我想在单个查找中计算所有总计，以使用SQLite查询而不是java代码来提高速度。

我只在SQLite中使用它，而不是在另一个引擎上。

Answer 1

使用Type，Total和Scrap列创建一个新表，然后使用单独的SQL语句插入所需的数据，如下所示：

第一步：使用以下列创建一个newTable :(类型，总计，废料）

第二步：运行以下语句：

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

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

或者如果您在一个查询中需要这些，您可以执行以下操作：

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

等...

你也可以多次加入同一张桌子并获得相同的结果：

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

SQL Totals分组在一列中

1 个答案: