Question

我以这种格式继承了一个树型表

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我想找到最终父母主题所在的所有StatementAreaIds，比如数学（即SubjectId = 110）。例如，如果SubjectId是Maths，我会在树中获得StatementAreaIds列表：

StatementAreaId | ParentStatementAreaId | SubjectId | Description
-----------------------------------------------------------------
1               | 0                     | 100       | Reading
2               | 0                     | 110       | Maths
3               | 2                     | 0         | Number
4               | 2                     | 0         | Shape
5               | 3                     | 0         | Addition
6               | 3                     | 0         | Subtraction

如果有帮助，树的最大深度为3。

由于

Answer 1

拯救的递归CTE：

创建并填充样本表：（请在将来的问题中将此步骤保存起来）

SslMode=None

查询：

DECLARE @T AS TABLE
(
    StatementAreaId int,
    ParentStatementAreaId int, 
    SubjectId int,
    Description varchar(20)
)

INSERT INTO @T VALUES
(1               , 0                     , 100       , 'Reading'),
(2               , 0                     , 110       , 'Maths'),
(3               , 2                     , 0         , 'Number'),
(4               , 2                     , 0         , 'Shape'),
(5               , 3                     , 0         , 'Addition'),
(6               , 3                     , 0         , 'Subtraction')

结果：

;WITH CTE AS 
(
    SELECT StatementAreaId, ParentStatementAreaId
    FROM @T 
    WHERE SubjectId = 110

    UNION ALL
    SELECT t1.StatementAreaId, t1.ParentStatementAreaId
    FROM @T t1 
    INNER JOIN CTE ON t1.ParentStatementAreaId = CTE.StatementAreaId
)

SELECT StatementAreaId
FROM CTE

查找树结构中的所有成员

1 个答案: