Sql 使用CTE从上一行值更新值

这个问题是我以前问题的一个变体。我希望用一个例子来解释这个问题。所以

样本数据 以下是要使用的示例数据：

DECLARE @Test TABLE (GID      int,             Seq     int, 
                     IsLive   bit,             Eff     date, 
                     Name     varchar(50),     Salary  decimal) 

INSERT INTO @Test VALUES (1, 1, 1, '01-08-2012', 'RTS', NULL)
INSERT INTO @Test VALUES (1, 2, 0, '01-09-2012', 'RTA', NULL)
INSERT INTO @Test VALUES (1, 3, 1, '01-10-2012', 'FSA', NULL)
INSERT INTO @Test VALUES (1, 4, 0, '01-11-2012',  NULL, NULL)
INSERT INTO @Test VALUES (1, 5, 1, '01-12-2012', 'FSA', NULL)
INSERT INTO @Test VALUES (2, 1, 1, '01-08-2012', 'RTS', NULL)
INSERT INTO @Test VALUES (2, 2, 0, '01-09-2012', 'RTA', NULL)
INSERT INTO @Test VALUES (2, 3, 1, '01-10-2012', 'FSA', NULL)
INSERT INTO @Test VALUES (2, 4, 0, '01-11-2012', 'GSM', NULL)
INSERT INTO @Test VALUES (2, 5, 1, '01-12-2012', 'FSA', NULL)
INSERT INTO @Test VALUES (3, 1, 1, '01-01-2012', 'FSA', NULL)
INSERT INTO @Test VALUES (3, 2, 0, '01-02-2012', NULL, NULL)
INSERT INTO @Test VALUES (4, 1, 1, '01-01-2012', NULL, NULL)
INSERT INTO @Test VALUES (4, 2, 0, '01-02-2012', 'FSA', NULL)
INSERT INTO @Test VALUES (4, 3, 0, '01-03-2012', NULL, NULL)
INSERT INTO @Test VALUES (5, 1, 0, '01-01-2012', NULL, NULL)
INSERT INTO @Test VALUES (5, 2, 1, '01-02-2012', 'LSI', NULL)
INSERT INTO @Test VALUES (5, 3, 0, '01-03-2012', NULL, NULL)
INSERT INTO @Test VALUES (6, 1, 1, '01-01-2012', NULL, NULL)
INSERT INTO @Test VALUES (6, 2, 0, '01-02-2012', 'LSI', NULL)
INSERT INTO @Test VALUES (6, 3, 1, '01-03-2012', NULL, NULL)

SELECT * FROM @Test

下面是两个示例结果集。尽管代码段显示插入，但重点是显示可接受的输出集的外观：

样本输出1 在下面的数据集中，当一行的IsLive=0时，其列中的值必须覆盖其下IsLive=1的行中相同列的值，跳过空值。忽略第一行IsLive=0之前的任何IsLive=1行

样本输出2 在下面的数据集中，当一行的IsLive=0时，其列中的值必须覆盖其下IsLive=1的行中相同列的值。具有NULL值的列从上一行获取值

    INSERT INTO @Test VALUES (1, 1, 1, '01-08-2012', 'RTS', NULL)
    INSERT INTO @Test VALUES (1, 2, 0, '01-09-2012', 'RTA', NULL)
    INSERT INTO @Test VALUES (1, 3, 1, '01-10-2012', 'RTA', NULL)
    -- <- the following row is different from prev
    INSERT INTO @Test VALUES (1, 4, 0, '01-11-2012', 'RTA', NULL) 
    INSERT INTO @Test VALUES (1, 5, 1, '01-12-2012', 'RTA', NULL)
    INSERT INTO @Test VALUES (2, 1, 1, '01-08-2012', 'RTS', NULL)
    INSERT INTO @Test VALUES (2, 2, 0, '01-09-2012', 'RTA', NULL)
    INSERT INTO @Test VALUES (2, 3, 1, '01-10-2012', 'RTA', NULL)
    INSERT INTO @Test VALUES (2, 4, 0, '01-11-2012', 'GSM', NULL)
    INSERT INTO @Test VALUES (2, 5, 1, '01-12-2012', 'GSM', NULL)
    INSERT INTO @Test VALUES (3, 1, 1, '01-01-2012', 'FSA', NULL)
    INSERT INTO @Test VALUES (3, 2, 0, '01-02-2012', 'FSA', NULL)
    INSERT INTO @Test VALUES (4, 1, 1, '01-01-2012', NULL, NULL)
    INSERT INTO @Test VALUES (4, 2, 0, '01-02-2012', 'FSA', NULL)
    INSERT INTO @Test VALUES (4, 3, 0, '01-03-2012', 'FSA', NULL)
    INSERT INTO @Test VALUES (5, 1, 0, '01-01-2012', NULL, NULL)
    INSERT INTO @Test VALUES (5, 2, 1, '01-02-2012', 'LSI', NULL)
    INSERT INTO @Test VALUES (5, 3, 0, '01-03-2012', 'LSI', NULL)
    INSERT INTO @Test VALUES (6, 1, 1, '01-01-2012', NULL, NULL)
    INSERT INTO @Test VALUES (6, 2, 0, '01-02-2012', 'LSI', NULL)
    INSERT INTO @Test VALUES (6, 3, 1, '01-03-2012', 'LSI', NULL)

    SELECT * FROM @Test AS FakedOutput_2

使用APPLY可以为您的测试用例工作。下面给出的结果与解决方案2相同

SELECT  t1.GID,
        t1.Seq,
        t1.IsLive,
        t1.Eff,
        CASE WHEN t1.IsLive = 0 THEN COALESCE(t1.Name, t3.Name) ELSE COALESCE(t3.Name, t1.Name) END AS Name,
        Salary
FROM    @Test T1
        OUTER APPLY
        (   SELECT  TOP 1 Name
            FROM    @Test T2
            WHERE   T2.GID = T1.GID
            AND     T2.Seq < T1.Seq
            AND     t2.IsLive = 0
            AND     t2.Name IS NOT NULL
            ORDER BY Seq DESC
        ) t3

编辑2

我在apply中稍微修改了查询，现在它将尝试查找最近的行，其中live=0且名称不为null，如果没有live=1的行（如GID=4），它将采用名称不为null的最近行：

UPDATE  @Test
SET     Name = CASE WHEN t1.IsLive = 0 THEN COALESCE(t1.Name, t3.Name) ELSE COALESCE(t3.Name, t1.Name) END
FROM    @Test T1
        OUTER APPLY
        (   SELECT  TOP 1 Name
            FROM    @Test T2
            WHERE   T2.GID = T1.GID
            AND     T2.Seq < T1.Seq
            AND     t2.Name IS NOT NULL
            ORDER BY t2.IsLive, Seq DESC
        ) t3

---

我花了一段时间才意识到，这个问题只是我先前发布的问题的一个小变化。离开键盘一段时间，我就看到了答案@GarethDs的回答也对此做出了贡献

;WITH CTE AS ( 
    SELECT  T.GID, T.SEQ, T.IsLive, Name, Salary 
    FROM    @Test T
    JOIN    ( SELECT   GID, MIN(Seq) Seq 
              FROM     @Test 
              GROUP BY GID     
            ) S ON T.GID = S.GID AND T.Seq = S.Seq

    UNION ALL 

    SELECT t.GID, t.SEQ, T.IsLive,
           CASE WHEN T.IsLive = 0 THEN COALESCE(T.Name, C.Name) 
                ELSE COALESCE(C.Name, T.Name) END,
           CASE WHEN T.IsLive = 0 THEN COALESCE(T.Salary, C.Salary) 
                ELSE COALESCE(C.Salary, T.Salary) END 
    FROM   CTE C
    JOIN   @Test T ON T.GID = C.GID AND T.SEQ = C.SEQ+1 
) 
--SELECT * FROM CTE ORDER BY CTE.GID, CTE.Seq
UPDATE T 
SET    Name   = C.Name,  
       Salary =  C.Salary
FROM   @Test T
JOIN   CTE C ON C.GID = T.GID AND C.Seq = T.SEQ

---

@马哈茂德：谢谢，我正在修改格式。@GilM你可能想试试这个，因为你已经搞定了上一个！我在更新帖子时弄得有点乱，我似乎无法格式化，或者更确切地说，我不知道如何格式化新添加的测试用例：谢谢！我又添加了几个测试用例。它适用于除一个Gid=3之外的所有人，因此此解决方案需要适用于n个列，因此最后是Salary列，但我还没有填充它。我不确定这个解决方案是否能做到这一点。

UPDATE  @Test
SET     Name = CASE WHEN t1.IsLive = 0 THEN COALESCE(t1.Name, t3.Name) ELSE COALESCE(t3.Name, t1.Name) END
FROM    @Test T1
        OUTER APPLY
        (   SELECT  TOP 1 Name
            FROM    @Test T2
            WHERE   T2.GID = T1.GID
            AND     T2.Seq < T1.Seq
            AND     t2.IsLive = 0
            AND     t2.Name IS NOT NULL
            ORDER BY Seq DESC
        ) t3

UPDATE  @Test
SET     Name = CASE WHEN t1.IsLive = 0 THEN COALESCE(t1.Name, t3.Name) ELSE COALESCE(t3.Name, t1.Name) END
FROM    @Test T1
        OUTER APPLY
        (   SELECT  TOP 1 Name
            FROM    @Test T2
            WHERE   T2.GID = T1.GID
            AND     T2.Seq < T1.Seq
            AND     t2.Name IS NOT NULL
            ORDER BY t2.IsLive, Seq DESC
        ) t3

;WITH CTE AS ( 
    SELECT  T.GID, T.SEQ, T.IsLive, Name, Salary 
    FROM    @Test T
    JOIN    ( SELECT   GID, MIN(Seq) Seq 
              FROM     @Test 
              GROUP BY GID     
            ) S ON T.GID = S.GID AND T.Seq = S.Seq

    UNION ALL 

    SELECT t.GID, t.SEQ, T.IsLive,
           CASE WHEN T.IsLive = 0 THEN COALESCE(T.Name, C.Name) 
                ELSE COALESCE(C.Name, T.Name) END,
           CASE WHEN T.IsLive = 0 THEN COALESCE(T.Salary, C.Salary) 
                ELSE COALESCE(C.Salary, T.Salary) END 
    FROM   CTE C
    JOIN   @Test T ON T.GID = C.GID AND T.SEQ = C.SEQ+1 
) 
--SELECT * FROM CTE ORDER BY CTE.GID, CTE.Seq
UPDATE T 
SET    Name   = C.Name,  
       Salary =  C.Salary
FROM   @Test T
JOIN   CTE C ON C.GID = T.GID AND C.Seq = T.SEQ