Sql server T-SQL选择与条件连接

假设我有3张桌子：

汽车

• 身份证

CarColorHistory

• 身份证
• 龋齿
• 彩色
• 修改日期

颜色：

• 身份证
• 颜色名称

我想选择所有汽车及其颜色，但重要的是，汽车的颜色是

CarColorHistory

表中最后修改的颜色

我需要使用join来完成此操作

例如：

汽车：

汽车颜色历史记录：

1 1 1 26/03/2012  -> (actual color, can be take by date or id)
2 1 2 25/03/2012
3 2 2 25/03/2012

颜色：

1 Blue
2 Red

我需要得到结果：（汽车id，颜色名称）

我试图通过加入Cars表和CarColorHistory表来实现，但我得到了所有颜色的汽车。我只需要实际的颜色（最后添加）

---

请帮助

这应该能帮到你：

SELECT c.id, (
    SELECT co.ColorName FROM Color co
    WHERE co.id = (
        SELECT TOP 1 ColorID FROM CarColorHistory
        WHERE CarID = c.id
        ORDER BY ModificationDate DESC
    )
 ) AS ColorName

试试这个：

select c.id, colorname
from cars c
inner join CarColorHistory h on c.id = h.CarID
inner join Color c2 on h.colorid = c2.id
where h.ModificationDate = (select max(ModificationDate)
                            from CarColorHistory x where c.id = x.CarId)

---

有几种方法可以得到结果。您可以使用子查询获取

max（modificationdate）

：

看

或者，由于您使用的是SQL Server，因此可以使用：

---

请参见

实现这一点的一种方法可能是只使用子查询，就像以前发布的一样，因为您使用的是t-sql，所以您还应该能够使用apply：

SELECT
        Cars.Id, LatestColors.ColorID, LatestColors.ModificationDate
    FROM Cars
    CROSS APPLY (
        SELECT TOP 1
                ColorID, ModificationDate
            FROM CarColorHistory
            WHERE CarID = Cars.ID
            ORDER BY ModificationDate DESC
    ) AS LatestColors

---

如果您有

Sql Server 2005

或更高版本，则可以尝试此操作：

您可以在此处尝试

通用表表达式的工作原理：

我不确定这是不是最好的方式，但这是我做这件事的方式。首先使用MAX从表中获取所需的值，然后将该结果作为表使用，以
联接
，以消除不需要的值

SELECT c.ID, Color.Color
From Cars c JOIN CarColorHistory h on c.id = h.CarID
     JOIN Color on h.ColorID = Color.ID
     JOIN

    --Create a table with only the latest value and the car ID
    ( 
    SELECT c.ID, Max(h.TimeStamp) as time
    FROM Cars c JOIN CarColorHistory h on c.id = h.CarID
         JOIN Color on h.ColorID = Color.ID
    Group by c.ID --Join the table on latest time to get rid of old timestamps
    ) Max on Max.ID = c.ID and h.TimeStamp=max.time

谢谢，但你能帮我加入声明吗？我怎样才能用你的浓咖啡？这对我的老师很重要。为什么您需要颜色历史记录的ID？谢谢，这正是我需要的：*
select c.id, r.colorname
from cars c
inner join CarColorhistory h1
  on c.id = h1.carid
inner join
(
  select max(modificationdate) MaxDate,
    carid
  from CarColorhistory
  group by carid
) h2
  on h1.carid = h2.carid
  and h1.modificationdate = h2.maxdate
inner join color r
  on h1.colorid = r.id

select id, colorname
from
(
  select c.id, r.colorname,
    row_number() over(partition by c.id order by modificationdate desc) rn
  from cars c
  inner join CarColorhistory h1
    on c.id = h1.carid
  inner join color r
    on h1.colorid = r.id
) src
where rn = 1;

SELECT
        Cars.Id, LatestColors.ColorID, LatestColors.ModificationDate
    FROM Cars
    CROSS APPLY (
        SELECT TOP 1
                ColorID, ModificationDate
            FROM CarColorHistory
            WHERE CarID = Cars.ID
            ORDER BY ModificationDate DESC
    ) AS LatestColors

  ;WITH CTE_Cars(CarID, MaxDate)
    AS
    (
    SELECT CarID, MAX(ModificataionDate) AS MaxDate
    FROM CarColorHistory
    GROUP BY CarID
    )
    SELECT CTE_Cars.CarID, Color.ColorName
    FROM 
    CTE_Cars
    INNER JOIN CarColorHistory ON CarColorHistory.CarID = CTE_Cars.CarID AND
    CarColorHistory.ModificataionDate = CTE_Cars.MaxDate
    INNER JOIN Color ON Color.id = CarColorHistory.ColorId

SELECT c.ID, Color.Color
From Cars c JOIN CarColorHistory h on c.id = h.CarID
     JOIN Color on h.ColorID = Color.ID
     JOIN

    --Create a table with only the latest value and the car ID
    ( 
    SELECT c.ID, Max(h.TimeStamp) as time
    FROM Cars c JOIN CarColorHistory h on c.id = h.CarID
         JOIN Color on h.ColorID = Color.ID
    Group by c.ID --Join the table on latest time to get rid of old timestamps
    ) Max on Max.ID = c.ID and h.TimeStamp=max.time