Question

我有3张桌子

表1和表2都通过“ ItemId”外键与表3关联

我想编写一个查询，该查询将基于这些表返回一些统计数据

表3提供了name列，其余部分来自其他两个

SELECT t1.ItemId, name, currentQuantity, previousQuantity, currentValue, previousValue
FROM (
  SELECT ItemId, SUM(quantity) as currentQuantity, SUM(quantity * purchaseNetPrice) AS currentValue
  FROM table_1
  GROUP BY ItemId
) AS t1
LEFT JOIN (
  SELECT ItemId, SUM(quantity) as previousQuantity, SUM(quantity * purchaseNetPrice) AS previousValue
  FROM table_2
  GROUP BY ItemId
) AS t2 ON t1.ItemId = t2.ItemId
INNER JOIN table_3 ON table_1.ItemId = table_3.ItemId

这将输出

ItemId | name |  currentQuantity  | previousQuantity| currentValue | previousValue
-------+------+-------------------+-----------------+--------------+---------------
 1     |ITEM1 | 4500              | 27000           | 523000       | 3240000       |
 2     |ITEM2 | 5800              | 15000           | 386000       | 2250000       |

这点还可以，但是我也想计算数量和价值的差异

ItemId | name |  currentQuantity  | previousQuantity| currentValue | previousValue | qDiff | valDiff
-------+------+-------------------+-----------------+--------------+---------------
 1     |ITEM1 | 4500              | 27000           | 523000       | 3240000       | diff  | diff
 2     |ITEM2 | 5800              | 15000           | 386000       | 2250000       | diff  | diff

具有以下逻辑：

数量差异-> currentQuantity-previousQuantity

值差-> currentValue-previousValue

我在哪里将其放在单个查询中？

Answer 1

您完全正确。我会使用子查询分解（WITH AS）来清理代码。

WITH t1_summary as
(
  SELECT ItemId, SUM(quantity) as currentQuantity, SUM(quantity * purchaseNetPrice) AS currentValue
  FROM table_1
  GROUP BY ItemId
),
t2_summary as (SELECT ItemId, SUM(quantity) as previousQuantity, SUM(quantity * purchaseNetPrice) AS previousValue
  FROM table_2
  GROUP BY ItemId
) 
SELECT t3.ItemId, name, currentQuantity, previousQuantity, currentValue, previousValue, currentQuantity - previousQuantity as quantity_difference, currentValue - previousValue as value_difference
from t3,t1_summary,t2_summary
where t1_summary.ItemId = t3.ItemId
and t2_summary.ItemId = t3.ItemId

Answer 2

计算外部SELECT中的其他列，并使用AS为它们添加别名：

SELECT t1.ItemId, 
       name, 
       currentQuantity, 
       previousQuantity, 
       currentValue, 
       previousValue, 
       currentQuantity - previousQuantity as qDiff, 
       currentValue - previousValue as valDiff 
FROM ....

如何在SQL中将求和值与联接一起添加

2 个答案: