Question

我有以下数据：SQL Fiddle (Schema)

/* Item */
CREATE TABLE [dbo].[Item](
    [ID] [int] IDENTITY(1,1) NOT NULL,
    [Description] [nvarchar](30) NOT NULL CONSTRAINT [DF_Item_Description]  DEFAULT (''),
    [ItemLookupCode] [nvarchar](25) NOT NULL CONSTRAINT [DF_Item_ItemLookupCode]  DEFAULT (''),
    [Price] [money] NOT NULL CONSTRAINT [DF_Item_Price]  DEFAULT (0),
    [LastUpdated] [datetime] NOT NULL CONSTRAINT [DF_Item_LastUpdated]  DEFAULT (getdate()),
    [DateCreated] [datetime] NOT NULL CONSTRAINT [Df_Item_DateCreated]  DEFAULT (getdate()),
 CONSTRAINT [PK_Item] PRIMARY KEY NONCLUSTERED 
(
    [ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) ON [PRIMARY]
) ON [PRIMARY]

GO

INSERT INTO [dbo].[Item] (
    [Description],
    [ItemLookupCode],
    [Price],
    [LastUpdated]
)
VALUES
  ('Product A1', 'PA1', 1, '03/01/2016 12:00:00'),
  ('Product A2', 'PA2', 2, '02/01/2016 12:00:00'),
  ('Product A3', 'PA3', 3, '01/01/2016 12:00:00'),

  ('Product B3', 'PB3', 3, '02/01/2016 12:00:00'),
  ('Product B2', 'PB2', 2, '03/01/2016 12:00:00'),
  ('Product B1', 'PB1', 1, '01/01/2016 12:00:00'),

  ('Product C2', 'PC2', 2, '02/01/2016 12:00:00'),
  ('Product C1', 'PC1', 1, '01/01/2016 12:00:00'),
  ('Product C3', 'PC3', 3, '03/01/2016 12:00:00')

GO

/* ItemClass */
CREATE TABLE [dbo].[ItemClass](
    [ID] [int] IDENTITY(1,1) NOT NULL,
    [Description] [nvarchar](30) NOT NULL CONSTRAINT [DF_ItemClass_Description]  DEFAULT (''),
    [ItemLookupCode] [nvarchar](25) NOT NULL CONSTRAINT [Df_ItemClass_ItemLookupCode]  DEFAULT (''),
    [Price] [money] NOT NULL CONSTRAINT [DF_ItemClass_Price]  DEFAULT ((0)),
 CONSTRAINT [PK_ItemClass] PRIMARY KEY NONCLUSTERED 
(
    [ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) ON [PRIMARY]
) ON [PRIMARY]

GO

INSERT INTO [dbo].[ItemClass] (
    [Description],
    [ItemLookupCode],
    [Price]
)
VALUES
  ('ItemClass A', 'ICA', 1),
  ('ItemClass B', 'ICB', 2),
  ('ItemClass C', 'ICC', 3)

GO

/* ItemClassComponent */
CREATE TABLE [dbo].[ItemClassComponent](
    [ID] [int] IDENTITY(1,1) NOT NULL,
    [ItemClassID] [int] NOT NULL CONSTRAINT [DF_ItemClassComponent_ItemClassID]  DEFAULT (0),
    [ItemID] [int] NOT NULL CONSTRAINT [DF_ItemClassComponent_ItemID]  DEFAULT (0),
    [Price] [money] NOT NULL CONSTRAINT [Df_ItemClassComponent_Price]  DEFAULT (0),
 CONSTRAINT [PK_ItemClassComponent] PRIMARY KEY NONCLUSTERED 
(
    [ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) ON [PRIMARY]
) ON [PRIMARY]

GO

INSERT INTO [dbo].[ItemClassComponent] (
    [ItemClassID],
    [ItemID],
    [Price]
)
VALUES
  (1, 1, 1),
  (1, 2, 1),
  (1, 3, 1),
  (2, 6, 1),
  (2, 5, 1),
  (2, 4, 1),
  (3, 8, 1),
  (3, 7, 1),
  (3, 9, 1)
GO

我正在尝试从 dbo.Item 中为每个最新更新的产品返回数据（在dbo.ItemClassComponent中定义）。

我已经非常接近了，但我的查询返回了重复的行！如此接近......有人能引导我朝着正确的方向前进吗？因为 - TBH我不知道为什么我看到重复的行返回lol。

我的尝试：SQL Fiddle

SELECT DISTINCT
    ic.Description
    ,i.ID
    ,i.Description
    ,i.ItemLookupCode
    ,i.Price
    ,i.LastUpdated
FROM Item i
INNER JOIN ItemClassComponent icc
    ON icc.ItemID = i.ID
INNER JOIN ItemClass ic
    ON ic.ID = icc.ItemClassID
INNER JOIN (
    SELECT
        MAX(_i.LastUpdated) AS LastUpdated
    FROM Item _i
    JOIN ItemClassComponent _icc
        ON _icc.ItemID = _i.ID
    GROUP BY _icc.ItemClassID
) lu
    ON lu.LastUpdated = i.LastUpdated;

注意： 我不想在那里拍打DISTINCT ......

Answer 1

我很确定您只需要比较项目类别以及上次更新日期：

app.routing.ts

通常，我会使用窗口函数来编写它：

[blueprintsDict writeToFile: [[NSString stringWithFormat:@"~/MbPatchBlueprints.plist"] stringByExpandingTildeInPath] atomically:YES];

使用多个联接时确定组中的上次更新行

1 个答案: