Question

我的表（名为Inventory）如下：

InventoryType，LocationID，InventoryLevel，SafetyStock，MaxLevel，ModifiedAt

Erasors，1,14,3,15,11-2014

Erasors，2,4,10,50,10-2014

Erasors，2,5,10,50,11-2014

铅笔，1,10,5,45,11-2014

铅笔，2,23,15,50,11-2014

笔，1,9,10,50,11-2014

笔，2,55,10,50,12-2014

有三个主键：InventoryType，LocationID和ModifiedAt。

给定指定的LocationID，我希望查询为每个不同的InventoryType返回all，其中返回的每个元组的日期是具有指定LocationID的给定库存类型的记录中的最新ModifiedAt日期。例如，LocationID = 2将返回：

InventoryType，LocationID，InventoryLevel，SafetyStock，MaxLevel，ModifiedAt

Erasors，2,5,10,50,11-2014

铅笔，2,23,15,50,11-2014

笔，2,55,10,50,12-2014

到目前为止，我的尝试如下：

SELECT InventoryType, LocationID, InventoryLevel,
       SafetyStock, MaxLevel, ModifiedAt
FROM Inventory
WHERE LocationID = 2 AND ModifiedAt IN
     (SELECT TOP 1 ModifiedAt 
      FROM Inventory
      WHERE LocationID = 2
      ORDER BY ModifiedAt DESC);

我的查询返回：

InventoryType,LocationID,InventoryLevel,SafetyStock,MaxLevel,ModifiedAt
Pens,2,55,10,50,12-2014

任何帮助都将不胜感激。

Answer 1

您需要一个相关的子查询。试试这个：

SELECT InventoryType, LocationID, InventoryLevel, SafetyStock, MaxLevel, ModifiedAt
FROM Inventory as i
WHERE LocationID = 2 AND
      ModifiedAt IN (SELECT TOP 1 i2.ModifiedAt
                     FROM Inventory as i2
                     WHERE i2.LocationID = 2 AND i2.InventoryType = i.InventoryType
                     ORDER BY i2.ModifiedAt DESC
                    );

Answer 2

使用SELECT DISTINCT选择不同的InventoryType。

SELECT DISTINCT InventoryType, LocationID, 
InventoryLevel, SafetyStock, MaxLevel, ModifiedAt
FROM Inventory
WHERE LocationID = 2
AND ModifiedAt IN 
(SELECT TOP 1 ModifiedAt FROM Inventory WHERE LocationID = 2 ORDER BY ModifiedAt DESC)

SQL嵌套查询，最大值，分组

2 个答案: