不使用 CTE 的父子层次结构路径

Question

您好，我有以下表格：

create table Features
(
FeatureId bigint,
FeatureName varchar(255),
ParentId bigint
)

insert into Features values(10, 'Feature 1', 1);
insert into Features values(11, 'Feature 2', 10);
insert into Features values(12, 'Feature 3', 11);
insert into Features values(13, 'Feature 4', 2);
insert into Features values(14, 'Feature 5', 13);

insert into Features values(15, 'Feature 6', 3);
insert into Features values(16, 'Feature 7', 15);
insert into Features values(17, 'Feature 8', 16);
insert into Features values(18, 'Feature 9', 17);
insert into Features values(19, 'Feature 10', 18);
insert into Features values(20, 'Feature 11', 19);
insert into Features values(21, 'Feature 12', 12);


create table Scenarios
(
ScenarioId bigint,
ParentId bigint,
ScenarioTitle varchar(25)
)

insert into Scenarios values(1, 0, 'Scenario 1')
insert into Scenarios values(2, 0, 'Scenario 2')
insert into Scenarios values(3, 0, 'Scenario 3')

在这里，一个特征可以有另一个特征作为父级，也可以有一个场景作为父级。对于场景，父 ID 可以是 0，也可以是其他场景。

我想得到每个特征的路径如下：

FeatureId   ParentId    FeatureName PathString          PathLength
10          1           Feature 1   1                   0
11          10          Feature 2   1/10                1
12          11          Feature 3   1/10/11             2
13          2           Feature 4   2                   0
14          13          Feature 5   2/13                1
15          3           Feature 6   3                   0
16          15          Feature 7   3/15                1
17          16          Feature 8   3/15/16             2
18          17          Feature 9   3/15/16/17          3
19          18          Feature 10  3/15/16/17/18       4
20          19          Feature 11  3/15/16/17/18/19    5
21          12          Feature 12  1/10/11/12          3

由于我想将此结果收集到临时表中以进行进一步处理，因此我尝试了 select into 并且 Azure SQL DW 抛出 Using SELECT INTO statement is not supported in Parallel Data Warehouse. Modify the statement and re-try executing it.

这是我的查询（可能不是很好，因为我仍在计算递归 sql）

drop table FeaturesWithPath;
;WITH FeaturePaths (FeatureId, ParentId, FeatureName, PathString)
AS
(
-- Anchor member definition
    SELECT g.FeatureId, g.ParentId, g.FeatureName, cast(CAST(g.ParentId as nvarchar(max)) as varchar(max)) as PathString
    FROM dbo.Features AS g
    UNION ALL
-- Recursive member definition
    SELECT g.FeatureId, g.ParentId, g.FeatureName, PathString + '/' + cast(g.ParentId as varchar(max))
    FROM dbo.Features AS g
    INNER JOIN FeaturePaths AS gp
        ON g.ParentId = gp.FeatureId
)

SELECT FeatureId, ParentId, FeatureName, PathString into FeaturesWithPath FROM FeaturePaths;
--select * from FeaturesWithPath order by FeatureId;

drop table FeaturesWithPathLength;
select *, LEN(PathString) - LEN(REPLACE(PathString, '/', '')) as PathLength into FeaturesWithPathLength from FeaturesWithPath
--select * from FeaturesWithPathLength order by FeatureId

drop table MaxFeaturePathLenghtRowTable;

select * into MaxFeaturePathLenghtRowTable
from FeaturesWithPathLength
where PathLength = (select max(PathLength) from FeaturesWithPathLength as f where f.FeatureId = FeaturesWithPathLength.FeatureId)
or PathLength = (select max(PathLength) from FeaturesWithPathLength as f where f.FeatureId = FeaturesWithPathLength.FeatureId
    and PathLength > (select max(PathLength) from FeaturesWithPathLength as f2 where f2.FeatureId = FeaturesWithPathLength.FeatureId));

--select * from MaxFeaturePathLenghtRowTable order by FeatureId

drop table FeaturesPerParentTable
select FeatureId, [value] as NewParentId, FeatureName, COALESCE(NULLIF(SUBSTRING(PathString, 0, CHARINDEX('/', PathString)), ''), [value]) AS ScenarioId into FeaturesPerParentTable
    from MaxFeaturePathLenghtRowTable 
    cross apply STRING_SPLIT (PathString, '/') cs order by FeatureId

select * from FeaturesPerParentTable order by FeatureId;

我尝试将 CTE 转换为使用 CTAS，但这也不起作用。

这就是我尝试 CTAS 的方式：

;WITH FeaturePaths (FeatureId, ParentId, FeatureName, PathString)
AS
(
-- Anchor member definition
    SELECT g.FeatureId, g.ParentId, g.FeatureName, cast(CAST(g.ParentId as nvarchar(max)) as varchar(max)) as PathString
    FROM dbo.Features AS g
    --WHERE parentId=0
    UNION ALL
-- Recursive member definition
    SELECT g.FeatureId, g.ParentId, g.FeatureName, PathString + '/' + cast(g.ParentId as varchar(max))
    FROM dbo.Features AS g
    INNER JOIN FeaturePaths AS gp
        ON g.ParentId = gp.FeatureId
)

CREATE TABLE #tmp_fct
WITH
(
    DISTRIBUTION = ROUND_ROBIN
)
AS
SELECT  FeatureId, ParentId, FeatureName, PathString
FROM    FeaturePaths;

现在我想知道是否有办法获取Azure SQL DW 上每个功能的路径并将结果收集到表格中。

-- 更新--

SQL中的解决方案see this

这是 C# 中的解决方案

void Main()
{
    var scenarios = new List<Scenario> {
        new Scenario{Id = 1, Title = "Scenario 1", ParentId = 0},
        new Scenario{Id = 2, Title = "Scenario 2", ParentId = 0},
        new Scenario{Id = 3, Title = "Scenario 3", ParentId = 0},
    };

    var features = new List<Feature> {
            new Feature{Id =10, Title = "Feature 1", ParentId =1},
            new Feature{Id =11, Title = "Feature 2", ParentId =10},
            new Feature{Id =12, Title = "Feature 3", ParentId =11},
            new Feature{Id =13, Title = "Feature 4", ParentId =2},
            new Feature{Id =14, Title = "Feature 5", ParentId =13},

            new Feature{Id =15, Title = "Feature 6", ParentId =3},
            new Feature{Id =16, Title = "Feature 7", ParentId =15},
            new Feature{Id =17, Title = "Feature 8", ParentId =16},
            new Feature{Id =18, Title = "Feature 9", ParentId =17},
            new Feature{Id =19, Title = "Feature 10", ParentId =18},
            new Feature{Id =20, Title = "Feature 11", ParentId =19},
            new Feature{Id =21, Title = "Feature 12", ParentId =12}
        };

    var scenarioIds = new HashSet<long>(scenarios.Select(x => x.Id));

    //get path
    IList<Feature> withPath = features.Select(x => { x.Path = GetPath(x, features, scenarioIds); return x; }).ToList().Dump("With path");
}

private string GetPath(Feature f, IList<Feature> features, HashSet<long> scenarioIds)
{
    if (scenarioIds.Contains(f.ParentId))
    {
        return f.ParentId.ToString();
    }
    else
    {
        var parent = features.First(d => d.Id == f.ParentId);
        return GetPath(parent, features, scenarioIds) + "/" + f.ParentId;
    }
}

public class Scenario
{
    public long Id { get; set; }
    public string Title { get; set; }
    public long ParentId { get; set; }
}

public class Feature
{
    public long Id { get; set; }
    public string Title { get; set; }
    public long ParentId { get; set; }
    public string Path { get; set; } //temp
}

Answer 1

由于目前 Azure SQL 数据仓库不支持递归 CTE 或游标，因此您可以使用良好的老式循环来执行此操作，例如：

-- Loop thru Features
DECLARE @counter INT = 1;

-- Insert first record where no parent exists
IF OBJECT_ID('tempdb..#features') IS NOT NULL DROP TABLE #features;

CREATE TABLE #features
WITH
    (
    DISTRIBUTION = HASH ( FeatureId ),
    LOCATION = USER_DB
    )
AS
WITH cte AS
(
SELECT 1 AS xlevel, p.FeatureId, p.ParentId, p.FeatureName, CAST( p.ParentId AS VARCHAR(255) ) AS PathString, 0 AS PathLength
FROM dbo.Features p
WHERE NOT EXISTS 
    (
    SELECT *
    FROM dbo.Features c
    WHERE p.ParentId = c.FeatureId
    )
)
SELECT *
FROM cte;


SELECT 'before' s, * FROM #features ORDER BY FeatureId;

-- Loop recursively through the child records
WHILE EXISTS (
SELECT *
    FROM #features p
        INNER JOIN dbo.features c ON p.FeatureId = c.ParentId
    WHERE p.xlevel = @counter
    )
BEGIN

    -- Insert next level
    INSERT INTO #features ( xlevel, FeatureId, ParentId, FeatureName, PathString, PathLength )
    SELECT @counter + 1 AS xlevel, c.FeatureId, c.ParentId, c.FeatureName, p.PathString + '/' + CAST( c.ParentId AS VARCHAR(255) ) AS PathString, @counter AS PathLength
    FROM #features p
        INNER JOIN dbo.features c ON p.FeatureId = c.ParentId
    WHERE p.xlevel = @counter;

    SET @counter += 1;

    -- Loop safety
    IF @counter > 99
    BEGIN 
        RAISERROR( 'Too many loops!', 16, 1 ) 
        BREAK 
    END;

END


SELECT 'after' s, *  FROM #features ORDER BY FeatureId;

包含设置的完整代码可用here。

我的结果：

希望对您有所帮助。

Answer 2

为什么不预先创建 FeaturesWithPath 表并使用以下伪代码插入其中？

CREATE TABLE FeaturesWithPath (FeatureId type, ParentId type, FeatureName type, PathString type)

;with FeaturePaths (FeatureId, ParentId, FeatureName, PathString)
AS
(
-- Anchor member definition
    SELECT g.FeatureId, g.ParentId, g.FeatureName, cast(CAST(g.ParentId as nvarchar(max)) as varchar(max)) as PathString
    FROM dbo.Features AS g
    UNION ALL
-- Recursive member definition
    SELECT g.FeatureId, g.ParentId, g.FeatureName, PathString + '/' + cast(g.ParentId as varchar(max))
    FROM dbo.Features AS g
    INNER JOIN FeaturePaths AS gp
        ON g.ParentId = gp.FeatureId
)
insert FeaturesWithPath (FeatureId, ParentId, FeatureName, PathString)
SELECT FeatureId, ParentId, FeatureName, PathString FROM FeaturePaths;