Tsql 从以前的记录继承值

在下表中，除了值之外的所有字段都是表上唯一索引的一部分。仅当记录具有空值时，我才希望将值从具有

ValueNULL

的记录继承到下一个修订记录（请参见下面的示例）：

Var[n]Value

字段使用varchar，我的表中可能有1-n个

Var[n]Value

字段

资料来源：

Document#   Revision    Project#    config# Var1Value   Var2Value
1744    1   2   1   NULL    NULL
1744    2   2   1   NULL    NULL
1744    3   2   1   Tit1    ABC
1744    4   2   1   Tit2    ABD
1744    5   2   1   NULL    NULL
1744    6   2   1   NULL    SDC
1744    7   2   1       AS
1744    8   2   1   Tit3    NULL

所需结果（注意修订记录5和6的更改

var1value

和5,8的更改

var2value

）：

你知道如何用SQL来处理它吗

请告知

我尝试了以下方法：

declare @TableName as VarChar(32) = 'MYTABLE'
declare @SetClause as VarChar(1024)
declare @LWhereClause as VarChar(1024)
declare @RWhereClause as VarChar(1024)

-- Get the column names.
select Column_Name
  into #Columns
  from Information_Schema.Columns
  where Table_Name = @TableName and Column_Name like 'Var%'
--select * from #Columns

-- Assemble the clauses we'll need for the   UPDATE   statement.
declare @ColumnName as VarChar(32)
while ( @@RowCount > 0 )
  begin
  select top 1 @ColumnName = Column_Name
    from #Columns
    order by Column_Name
  set @SetClause = case when @SetClause is NULL then '' else @SetClause + ', ' end +
    @ColumnName + ' = Coalesce( L.' + @ColumnName + ', R.' + @ColumnName + ' )'
  set @LWhereClause = case when @LWhereClause is NULL then '' else @LWhereClause + ' or ' end +
    'L.' + @ColumnName + ' is NULL'
  set @RWhereClause = case when @RWhereClause is NULL then '' else @RWhereClause + ' or ' end +
    'R.' + @ColumnName + ' is not NULL'
  delete from #Columns
    where Column_Name = @ColumnName
  end

--select @SetClause, @LWhereClause, @RWhereClause

-- Put together the   UPDATE   statement.
declare @Update as nVarChar(max)
set @Update=''
set @Update=@Update +
  'update L set ' + @SetClause + ' from ' + @TableName +
  ' as L inner join ' + @TableName + ' as R on R.DocId = L.DocId and R.Rev = L.Rev - 1 and R.Proj = L.Proj and R.Conf = L.Conf' +
  ' where ( ' + @LWhereClause + ' ) and ( ' + @RWhereClause + ' )'

-- Put together the entire loop.  This needs work.
declare @Loop as nVarChar(max)
set @Loop =''
set @Loop=@Loop+
  '@declare Eleanor as Int = 42;
    while ( @Eleanor > 0 ) ' 
    + @Update + ' 
    set @Eleanor = @@RowCount
    end'

--select @Loop

-- Execute it.
exec @Loop

drop table #Columns

我在exec循环中得到以下错误。为什么要截断nvarchar字符串

味精203，16级，状态2，第53行
名称'@声明埃莉诺为Int=42
而（@Eleanor>0）更新L集合variable104=聚结（L.variable104，R.variable104），variable105=聚结（L.variable105，R.variable105），variable106=聚结（L.variable106，R.variable106），variable107=聚结（L.variable107，R.variable107），variable112=聚结（L.variable112，R.variable112），variable116=聚结（L.variable116，R.variable116），variable119=聚结（L.variable119，R.variable119），variable120=聚结（L.variable120，R.variable120），variable121=聚结（L.variable121，R.variable121），variable122=聚结（L.variable122，R.variable122），variable124=Co'不是有效标识符

---

<> > >编辑< /强>：请原谅，但我没有考虑变量列。

此查询将检索在

YourTable

中定义的列：

select Column_Name from Information_Schema.Columns where Table_Name = 'YourTable'

此后，您需要构建一个动态查询并执行它。您可以为每个单独的列编写如下所示的代码，或者一次性处理所有列

---

动态构建查询是一个有点乏味的过程

declare @TableName as VarChar(32) = 'YourTable'
declare @SetClause as VarChar(1024)
declare @LWhereClause as VarChar(1024)
declare @RWhereClause as VarChar(1024)

-- Get the column names.
select Column_Name
  into #Columns
  from Information_Schema.Columns
  where Table_Name = @TableName and Column_Name like 'Var%'
select * from #Columns

-- Assemble the clauses we'll need for the   UPDATE   statement.
declare @ColumnName as VarChar(32)
while ( @@RowCount > 0 )
  begin
  select top 1 @ColumnName = Column_Name
    from #Columns
    order by Column_Name
  set @SetClause = case when @SetClause is NULL then '' else @SetClause + ', ' end +
    @ColumnName + ' = Coalesce( L.' + @ColumnName + ', R.' + @ColumnName + ' )'
  set @LWhereClause = case when @LWhereClause is NULL then '' else @LWhereClause + ' or ' end +
    'L.' + @ColumnName + ' is NULL'
  set @RWhereClause = case when @RWhereClause is NULL then '' else @RWhereClause + ' or ' end +
    'R.' + @ColumnName + ' is not NULL'
  delete from #Columns
    where Column_Name = @ColumnName
  end

select @SetClause, @LWhereClause, @RWhereClause

-- Put together the   UPDATE   statement.
declare @Update as VarChar(4096) =
  'update L set ' + @SetClause + ' from ' + @TableName +
  ' as L inner join ' + @TableName + ' as R on R.DocId = L.DocId and R.Rev = L.Rev - 1 and R.Proj = L.Proj and R.Conf = L.Conf' +
  ' where ( ' + @LWhereClause + ' ) and ( ' + @RWhereClause + ' )'

-- Put together the entire loop.  This needs work.
declare @Loop as VarChar(4096) =
  '@declare Eleanor as Int = 42; ...' + @Update + '...'

select @Loop

-- Execute it.
exec @Loop

drop table #Columns

---

这里有一种可怕的方法是基于版本号密集：

declare @Docs as Table ( DocId Int, Rev Int, Proj Int, Conf Int, Var1 VarChar(10) Null, Var2 VarChar(10) Null )

insert into @Docs ( DocId, Rev, Proj, Conf, Var1, Var2 ) values
  ( 1744, 1, 2, 1, NULL, NULL ),
  ( 1744, 2, 2, 1, NULL, NULL ),
  ( 1744, 3, 2, 1, 'Tit1', 'ABC' ),
  ( 1744, 4, 2, 1, 'Tit2', 'ABD' ),
  ( 1744, 5, 2, 1, NULL, NULL ),
  ( 1744, 6, 2, 1, NULL, 'SDC' ),
  ( 1744, 7, 2, 1, '', 'AS' ), -- The example data for this row is unclear.
  ( 1744, 8, 2, 1, 'Tit3', NULL )

select * from @Docs

declare @Eleanor as Int = 42
while ( @Eleanor > 0 )
  begin
  update L
    set Var1 = Coalesce( L.Var1, R.Var1 ), Var2 = Coalesce( L.Var2, R.Var2 )
    from @Docs as L inner join
      @Docs as R on R.DocId = L.DocId and R.Rev = L.Rev - 1 and R.Proj = L.Proj and R.Conf = L.Conf
    where ( L.Var1 is NULL or L.Var2 is NULL ) and ( R.Var1 is not NULL or R.Var2 is not NULL )
  set @Eleanor = @@RowCount
  end

select * from @Docs

以下文件的准确副本：

---

p、 s：我没有评论的特权。所以我写了答案。

修订号总是密集的吗？我不知道你说的密集是什么意思？修订是唯一索引的一部分（由文档#、修订、项目#和配置#组成）。我只需要根据以前修订的val[n]进行更新如果该值不为null，且相应当前修订的var[n]值为null，“密集”指的是一系列没有间隙的值。如果修订号密集，则给定一个大于1的值R，您可以始终指望表中的值R-1（对于同一文档和项目）。如果修订不密集，那么您需要继续搜索小于R的最大值。甚至可能没有修订版本！好的，我明白了。修订版本密集。谢谢Mahmood，我正在寻找一种动态方法，以便在我的示例中对n个varvalue字段进行查询。您能提供一个这样做的示例吗？如何进行在上面的例子中，我使用了var1和var2，但是当运行我的程序时，它可能运行在一个有100个变量的数据库上（即var100）在某些情况下，只有很少的变量。我正在寻找一种动态的方法来处理它，即使它运行了几个小时。我确实编辑了我的答案，以包含关于动态构建查询的附加信息。

declare @Docs as Table ( DocId Int, Rev Int, Proj Int, Conf Int, Var1 VarChar(10) Null, Var2 VarChar(10) Null )

insert into @Docs ( DocId, Rev, Proj, Conf, Var1, Var2 ) values
  ( 1744, 1, 2, 1, NULL, NULL ),
  ( 1744, 2, 2, 1, NULL, NULL ),
  ( 1744, 3, 2, 1, 'Tit1', 'ABC' ),
  ( 1744, 4, 2, 1, 'Tit2', 'ABD' ),
  ( 1744, 5, 2, 1, NULL, NULL ),
  ( 1744, 6, 2, 1, NULL, 'SDC' ),
  ( 1744, 7, 2, 1, '', 'AS' ), -- The example data for this row is unclear.
  ( 1744, 8, 2, 1, 'Tit3', NULL )

select * from @Docs

declare @Eleanor as Int = 42
while ( @Eleanor > 0 )
  begin
  update L
    set Var1 = Coalesce( L.Var1, R.Var1 ), Var2 = Coalesce( L.Var2, R.Var2 )
    from @Docs as L inner join
      @Docs as R on R.DocId = L.DocId and R.Rev = L.Rev - 1 and R.Proj = L.Proj and R.Conf = L.Conf
    where ( L.Var1 is NULL or L.Var2 is NULL ) and ( R.Var1 is not NULL or R.Var2 is not NULL )
  set @Eleanor = @@RowCount
  end

select * from @Docs