如何使用 while 循环遍历 table 并创建另一个具有所需值的 table

Question

我有两个 table：MainTable 和 MyTable。 MyTable 具有唯一的 ControlNo 和 ID。我需要首先添加 EffDate 从 MainTable 到 MyTable 基于 ID 和 ControlNo.

为此，我需要查看 PreviousID 列，然后查看 PreviousID 是否在 ID 列中，依此类推。

所需的输出应如下所示：

下面是一个示例，其中包含通过提供 ID 值来获得正确 EffDate 的虚拟数据。它有效，但我如何循环遍历整个 MainTable，将 ID 和 EffDate 检索到单独的 table，然后将 table 加入 MyTable?

-- function returns PreviousID based on ID
CREATE FUNCTION [dbo].[GetPriorQuoteID](@ID varchar(50))
RETURNS varchar(50)
AS
BEGIN
    DECLARE @RetVal varchar(50)
    SET @RetVal = NULL
    
    SELECT TOP 1 @RetVal = MainTable.PreviousID
    FROM         MainTable
    WHERE        MainTable.ID = @ID
    
    RETURN @RetVal
END

    -- create sample table
    IF OBJECT_ID('MainTable') IS NOT NULL DROP TABLE MainTable;
    select 3333 as ControlNo, 'QuoteID3' as ID, 'QuoteID2' as PreviousID, '2020-08-25' as EffDate 
    into MainTable
    union all select 2222 as COntrolNo, 'QuoteID2', 'QuoteID1', '2019-08-25'
    union all select 1111 as COntrolNo, 'QuoteID1', NULL, '2018-08-25'
    union all select 7777 as COntrolNo, 'QuoteID6', 'QuoteID5', '2020-02-10'
    union all select 6666 as COntrolNo, 'QuoteID5', NULL, '2019-02-10'
    select * from MainTable
    
    
    DECLARE @PriorQuote varchar(50)
    DECLARE @RetVal VARCHAR(50) = ''
    DECLARE @ControlNo INT
    DECLARE @ID varchar(50) = 'QuoteID3'
    
    SELECT TOP 1 @ControlNo = MainTable.ControlNo FROM MainTable WHERE MainTable.ID = @ID
    Set @PriorQuote = @ID
    
    SELECT TOP 1 @PriorQuote = MainTable.ID FROM MainTable WHERE MainTable.ControlNo = @ControlNo 
    
    WHILE dbo.GetPriorQuoteID(@PriorQuote) IS NOT NULL AND dbo.GetPriorQuoteID(@PriorQuote)<> @PriorQuote
    BEGIN
            SET @PriorQuote = dbo.GetPriorQuoteID(@PriorQuote)
        END
    
    
    SELECT TOP 1 @RetVal = CONVERT(VARCHAR(10), MainTable.EffDate, 101)
    FROM         MainTable
    WHERE        MainTable.ID = @PriorQuote
    SELECT @RetVal
    
    -- clean up
    drop table MainTable
    drop function GetPriorQuoteID

更新：添加虚拟数据 tables

-- create sample table #MainTable
IF OBJECT_ID('tempdb..#MainTable') IS NOT NULL DROP TABLE #MainTable;
create table #MainTable (ControlNo int, ID varchar(50), PreviousID varchar(50), EffDate date)
insert into #MainTable values
(3333,'QuoteID3','QuoteID2', '2020-08-25'),
(2222,'QuoteID2','QuoteID1', '2019-08-25'),
(1111,'QuoteID1',NULL, '2018-08-25'),
(7777,'QuoteID6','QuoteID5', '2020-02-10'),
(6666,'QuoteID5',NULL, '2019-02-10')
--select * from #MainTable

-- create sample table #MyTable
IF OBJECT_ID('tempdb..#MyTable') IS NOT NULL DROP TABLE #MyTable;
create table #MyTable (ControlNo int, ID varchar(50), EffDate date)
insert into #MyTable values 
(3333,'QuoteID3',NULL),
(7777,'QuoteID6',NULL)
--select * from #MyTable

Answer 1

您可以为此使用递归 CTE：

WITH cte 
AS
(

SELECT m.ID,m.PreviousID
FROM MainTable m
JOIN MainTable m2
     ON m.previousID = m2.ID
WHERE m2.previousID IS NULL

UNION ALL

SELECT m2.ID,cte.previousID
FROM cte
JOIN MainTable m2
     ON m2.previousID = cte.ID

)

SELECT *
FROM cte;

Answer 2

像下面这样使用 CTE 你可以获得想要的结果。 See live demo

了解有关递归 CTE 的更多信息here

 ; with cte as 
   (
       select EffDate, ControlNo, ID, Level=1 from MainTable
       where PreviousID is NULL
       union all
       select C.EffDate, M.ControlNo, M.ID, Level=Level+1 from MainTable AS M
       join cte as C on C.ID=M.PreviousID
     )
     
    select MyTable.*,cte.EffDate from cte join MyTable on Mytable.ID=cte.ID

Answer 3

您可以使用递归查询遍历层次结构。

我首先将原始 table 与主 table 连接起来，这将路径限制为我们感兴趣的行。然后，您可以递归到父级。最后，我们需要过滤每个路径的顶级父级：top() 和 row_number() 派上用场。

考虑：

with cte as (
    select t.controlno, t.id, m.previousid, m.effdate, 1 lvl 
    from #maintable m
    inner join #mytable t on t.controlno = m.controlno and t.id = m.id
    union all
    select c.controlno, c.id, m.previousid, m.effdate, c.lvl + 1
    from cte c
    inner join #maintable m on m.id = c.previousid
)
select top(1) with ties controlno, id, effdate
from cte 
order by row_number() over(partition by controlno, id order by lvl desc)

Demo on DB Fiddle:

controlno | id       | effdate   
--------: | :------- | :---------
     3333 | QuoteID3 | 2018-08-25
     7777 | QuoteID6 | 2019-02-10

Answer 4

这是 CTE 方法的工作示例，其中 table 提供了

;with recur_cte(ControlNo, ID, PreviousID, EffDate, HLevel) as (
    select mt.ControlNo, cast(null as varchar(100)), mt.PreviousID, mt.EffDate, 1
    from MainTable mt
    where not exists(select 1 
                     from MainTable mt_in
                     where mt.ID=mt_in.PreviousID)
    union all
    select rc.ControlNo, rc.ID, mt.PreviousID, mt.EffDate, rc.HLevel+1
    from recur_cte rc
         join MainTable mt on rc.PreviousID=mt.ID and rc.EffDate>mt.EffDate)
select * from recur_cte;

结果

ControlNo   ID  PreviousID  EffDate HLevel
3333    NULL    QuoteID2    2020-08-25  1
7777    NULL    QuoteID5    2020-02-10  1
7777    NULL    NULL        2019-02-10  2
3333    NULL    QuoteID1    2019-08-25  2
3333    NULL    NULL        2018-08-25  3

如何使用 while 循环遍历 table 并创建另一个具有所需值的 table

How to loop through table using while loop and create another table with values needed

sql

tsql

sql-server

datetime

recursive-query