SQL Server 中的递归循环答案

【问题标题】：Recursive Loop in SQL ServerSQL Server 中的递归循环
【发布时间】：2016-10-19 05:51:07
【问题描述】：

我有一个名为 WarehouseStore.dws6.BeScheduleItem 的表。下面是在 WarehouseStore.dws6.BeScheduleItem 中找到的数据的屏幕截图。 WarehouseStore.dws6.BeScheduleItem

我的要求是根据以下条件从 WarehouseStore.dws6.BeScheduleItem 表中找到缺失的节点。

将所有 isMissing 设置为 0
如果子字段具有 IcpUid 字段不为 NULL 并且父级具有 IcpUid 字段 NULL 然后将子父级 IsMissing 设置为 1。
如果子字段具有 IcpUid 字段 NULL 并且父级具有 IcpUid 字段 NULL 并且父级子级具有 IsMissing 等于 1 然后将子父级 IsMissing 设置为 1。
重复第 3 步，直到没有更多内容需要更新。

我能够在我的 SQL 代码中满足步骤 1 到 3，但没有满足步骤 4，因为我需要执行一个 for 循环来检查是否没有更多更新。下面是我的 SQL 代码

DECLARE @TEMP TABLE (
Code NVARCHAR(MAX) NOT NULL,
Name NVARCHAR(MAX) NULL,
Level INT NULL,
IsMissing BIT NULL,
ParentCode NVARCHAR(MAX) NULL,
IcpUid NVARCHAR(MAX) NULL
);

INSERT INTO @TEMP(
Code,
Name,
Level,
IsMissing ,
ParentCode ,
IcpUid 
)
SELECT 
Code,
Name,
Level,
IsMissing = 0,
ParentCode, 
IcpUid
FROM WarehouseStore.dws6.BeScheduleItem 
WHERE IsDeleted = 0
;

UPDATE P SET IsMissing = 1
FROM @TEMP C
INNER JOIN @TEMP P ON P.Code = C.ParentCode
WHERE C.IcpUid IS NOT NULL 
AND P.IcpUid IS NULL
;
SELECT 
P.Code,
P.Name,
P.Level,
C.IsMissing ,
C.ParentCode ,
P.IcpUid 
FROM @TEMP P
INNER JOIN @TEMP C ON P.Code = C.ParentCode
WHERE C.IsMissing = 1
AND C.IcpUid IS NULL 
AND P.IcpUid IS NULL
ORDER BY LEVEL

您能否建议我如何从上述代码构建递归循环。请注意：需要循环第 3 步，当前数据可能不需要它，但我们正在针对所有情况进行编码，而不仅仅是当前数据

【问题讨论】：

标签： sql-server recursion business-intelligence

【解决方案1】：

使用WHILE 或CURSOR。示例光标：

DECLARE @code VARCHAR(50) DECLARE db_cursor CURSOR FOR SELECT Code FROM WarehouseStore.dws6.BeScheduleItem WHERE IsDeleted = 0

OPEN db_cursor FETCH NEXT FROM db_cursor INTO @code

WHILE @@FETCH_STATUS = 0 BEGIN

UPDATE ... INNER JOIN ... P ON P.Code = @code WHERE C.IcpUid IS NOT NULL AND P.IcpUid IS NULL

FETCH NEXT FROM db_cursor INTO @name END CLOSE db_cursor DEALLOCATE db_cursor

【讨论】：

【解决方案2】：

这是我正在寻找的代码。

DECLARE @TMP TABLE
(
Code varchar(40),
Name varchar(120),
level int,
ParentCode varchar(40),
IcpUid varchar(32),
IsMIssing bit
);
DECLARE @NumCount INT = 0;
INSERT INTO @TMP
SELECT
    Code,
    Name,
    level,
    ParentCode,
    IcpUid,
    IsMissing
FROM WarehouseStore.dws6.BeScheduleItem
WHERE isdeleted = 0
AND name not like '%DELETED%';
--Step 2
MERGE INTO @TMP TGT USING (
SELECT DISTINCT 
   P.Code,
   IsMissing = 1
FROM @TMP C
INNER JOIN @TMP P ON P.Code = C.ParentCode
WHERE C.IcpUid IS NOT NULL
AND P.IcpUid IS NULL
) SRC
ON TGT.Code = SRC.Code
WHEN MATCHED THEN UPDATE SET TGT.IsMissing = SRC.IsMissing;
--Step 3
SET @NumCount = (SELECT COUNT(DISTINCT P.Code)
FROM @TMP C
INNER JOIN @TMP P on P.Code = C.ParentCode
WHERE C.IcpUid IS NULL 
AND P.IcpUid IS NULL 
AND C.IsMIssing = 1
  AND C.IsMissing <> P.IsMissing);
WHILE (@NumCount > 0)
BEGIN
--loop
MERGE INTO @TMP TGT USING (
SELECT DISTINCT 
P.Code,
IsMissing = 1
FROM @TMP C
INNER JOIN @TMP P ON P.Code = C.ParentCode
WHERE C.IcpUid IS NULL 
AND P.IcpUid IS NULL 
AND C.IsMIssing = 1
AND C.IsMissing <> P.IsMissing
) SRC
ON TGT.Code = SRC.Code
WHEN MATCHED THEN UPDATE SET TGT.IsMissing = SRC.IsMissing;
SET @NumCount = (SELECT COUNT(DISTINCT P.Code)
FROM @TMP C
INNER JOIN @TMP P on P.Code = C.ParentCode
WHERE C.IcpUid IS NULL 
AND P.IcpUid IS NULL 
AND C.IsMIssing = 1 
  AND C.IsMissing <> P.IsMissing );
END --end loop

SELECT *
FROM @TMP C
WHERE IsMissing = 1
ORDER BY Level;

【讨论】：