Question

@@ Version 1

使用SQL Server 2008，我试图将值级联到列中。我有一个包含组ID（GID）和Seq的表，其中包含组内记录的排序。对于存在的列，在本例中为Name和Salary - 我的真实表有超过50列，如果它们包含NULL，我需要使用包含非空值的该列的前一行的值更新NULL值。

这可以用来说明这一点：

GID Seq Name    Salary
1   1   James   NULL
1   2   NULL    100
1   3   NULL    NULL
2   1   NULL    81
2   2   Smith   NULL
2   3   NULL    NULL
3   1   Charles NULL
3   2   NULL    NULL
3   3   Brown   NULL
3   4   NULL    75
4   0   Ron 50
4   1   NULL    20
4   2   NULL    NULL

我的结果应该是：

GID Seq Name    Salary
1   1   James   NULL
1   2   James   100
1   3   James   100
2   1   NULL    81
2   2   Smith   81
2   3   Smith   81
3   1   Charles NULL
3   2   Charles NULL
3   3   Brown   NULL
3   4   Brown   75
4   0   Ron 50
4   1   Ron 20
4   2   Ron 20

我希望在不使用动态SQL，循环或游标的情况下执行此操作。

简单测试用例的代码：

DECLARE @Test TABLE (GID int, Seq int, Name varchar(50), Salary decimal) 

INSERT INTO @Test VALUES (1, 1, 'James', NULL)
INSERT INTO @Test VALUES (1, 2, NULL, 100.40)
INSERT INTO @Test VALUES (1, 3, NULL, NULL)
INSERT INTO @Test VALUES (2, 1, NULL, 80.50)
INSERT INTO @Test VALUES (2, 2, 'Smith', NULL)
INSERT INTO @Test VALUES (2, 3, NULL, NULL)
INSERT INTO @Test VALUES (3, 1, 'Charles', NULL)
INSERT INTO @Test VALUES (3, 2, NULL, NULL)
INSERT INTO @Test VALUES (3, 3, 'Brown', NULL)
INSERT INTO @Test VALUES (3, 4, NULL, 75)
INSERT INTO @Test VALUES (4, 0, 'Ron', 50)
INSERT INTO @Test VALUES (4, 1, NULL, 20)
INSERT INTO @Test VALUES (4, 2, NULL, NULL)

SELECT * FROM @Test

@@版本2 感谢GilM为@@版本1提供解决方案。我对此问题做了一些补充。 Seq列中的起始编号可以是0或1.在第一个问题的解决方案中，递归CTE中的锚点引用1，如果它是1或0怎么办？最后3行数据（GID = 4）被添加到此版本中的所有上述三个代码块中。

谢谢！

Answer 1

这个怎么样？：

;WITH CTE AS (
SELECT GID, SEQ, Name, Salary
FROM @Test t1
WHERE SEQ = (SELECT MIN(SEQ) FROM @Test t2 WHERE t2.GID = t1.GID)
UNION ALL
SELECT t.GID, t.SEQ, COALESCE(t.Name,c.Name), COALESCE(t.Salary,c.Salary)
FROM CTE c
JOIN @Test t ON t.GID = c.GID AND t.SEQ = c.SEQ+1
)
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

Answer 2

update T set
  Name =   (
           select top(1) T1.Name
           from @Test as T1
           where T1.GID = T.GID and
                 T1.Seq <= T.Seq and
                 T1.Name is not null
           order by T1.Seq desc
           ),
  Salary = (
           select top(1) T1.Salary
           from @Test as T1
           where T1.GID = T.GID and
                 T1.Seq <= T.Seq and
                 T1.Salary is not null
           order by T1.Seq desc
           )
from @Test as T
where T.Name is null or 
      T.Salary is null

有50列会有很多打字和很多相关的子查询。

这是一个使用XML的版本。较少的打字和性能可以更好。

with C as
(
  select GID,
         (
         select *
         from @Test as T2
         where T1.GID = T2.GID
         order by T2.Seq desc
         for xml path('row'), type
         ) as X
  from @Test as T1
  group by GID
)
update T set
       Name   = C.X.value('(/row[Seq<=sql:column("T.Seq")]/Name)[1]',   'varchar(50)'),
       Salary = C.X.value('(/row[Seq<=sql:column("T.Seq")]/Salary)[1]', 'decimal')
from @Test as T
  inner join C 
    on T.GID = C.GID

SE-Data

从上一行中的非空值更新空列值

2 个答案: