Question

我有这个存储过程：

ALTER PROCEDURE [dbo].[Get_All_Items]
AS
BEGIN
    SELECT
        ItemID, ItemName, CategoryID, CountryID,
        ItemSize, ColorID, ProductionDate, ExpiryDate, 
        UnitName, FirstUnitBarcode, FirstItemQuantity, 
        FirstUnitDefult, FirstUnitLimit, 
        UnitsTbl.SecondUnit, SecondUnitBarcode, SecondItemQuantity, 
        SecondUnitDefult, SecondUnitLimit, 
        ThirdUnit, ThirdUnitBarcode, ThirdItemQuantity, 
        ThirdUnitDefult, ThirdUnitLimit, UnitDefult, 
        ItemImage, ItemStatus, ItemsMainTbl.Nots,
        ItemsMainTbl.CreatedBy, ItemsMainTbl.CreatedDate, 
        ItemsMainTbl.ModifiedBy, ItemsMainTbl.ModifiedDate 
    FROM 
        ItemsMainTbl  
    INNER JOIN
        UnitsTbl ON ItemsMainTbl.FirstUnit = UnitsTbl.UnitID 
    INNER JOIN
        UnitsTbl ON ItemsMainTbl.SecondUnit = UnitsTbl.UnitID 
END

条件：

ItemsMainTbl.FirstUnit = UnitsTbl.UnitID
ItemsMainTbl.SecondUnit = UnitsTbl.UnitID
ItemsMainTbl.ThirdUnit = UnitsTbl.UnitID

如何在该公共列上连接所有三个表？

我只得到第一个

ItemsMainTbl.FirstUnit = UnitsTbl.UnitID

谢谢

Answer 1

如果要多次连接同一个表，则需要为连接表的每个实例指定别名，如下所示：

SELECT *
FROM ItemsMainTbl  
INNER JOIN UnitsTbl u1 ON ItemsMainTbl.FirstUnit = u1.UnitID 
INNER JOIN UnitsTbl u2 ON ItemsMainTbl.SecondUnit = u2.UnitID 
INNER JOIN UnitsTbl u3 ON ItemsMainTbl.ThirdUnit = u3.UnitID

然后在select语句中，您可以区分已连接的实例，如下所示：

SELECT u1.Barcode, -- Barcode from FirstUnit
       u2.Barcode, -- Barcode from SecondUnit
       u3.Barcode  -- Barcode from ThirdUnit

Answer 2

您需要为UnitsTbl定义参考。根据OOP，将这些引用视为同一类的新对象。此外，每次查询表时都使用引用是一个好习惯。

SELECT *
FROM 
    ItemsMainTbl t1
INNER JOIN
    UnitsTbl u1 ON t1.FirstUnit = u1.UnitID 
INNER JOIN
    UnitsTbl u2 ON t1.SecondUnit = u2.UnitID 
INNER JOIN 
    UnitsTbl u3 ON t1.ThirdUnit = u3.UnitID

内部加入存储过程

2 个答案: