Question

我有一个类似于这个

的数据库层次结构

LHID | location     | parent
------------------------------
1    | Trim         | NULL
2    | Trim - South | Trim
3    | South-1      | Trim - South

我需要做的是选择Trim - South的所有孩子。它非常深，有大约100个孩子的位置，我已经找到了递归方式，但没有运气复制它们。我知道通过递归方式选择所有子项的逻辑，因为我已经在其他语言中执行了类似的过程，从来没有使用过SQL，所以我很难掌握它的确切必要语法。有什么想法吗？

Answer 1

您可以使用递归CTE：

WITH CTE 
AS(
  SELECT 1 AS relationLevel, child.*
  FROM dbo.TableName child
  WHERE child.parent = 'Trim - South'

  UNION ALL

  SELECT relationLevel+1, parent.*
  FROM CTE nextOne
  INNER JOIN  dbo.TableName parent ON parent.parent = nextOne.location
)
SELECT * FROM CTE ORDER BY relationLevel

结果：

RELATIONLEVEL   LHID    LOCATION    PARENT
1                3      South-1     Trim - South
1                4      South-2     Trim - South
2                4      South-2-1   South-2

的 DEMO

也许你想从父母到孩子的travserse，然后使用：

WITH CTE AS( SELECT 1 AS relationLevel, parent.* FROM dbo.TableName parent WHERE parent.location = 'Trim - South' UNION ALL SELECT relationLevel + 1, child.* FROM CTE nextOne INNER JOIN dbo.TableName child ON child.parent = nextOne.location ) SELECT * FROM CTE ORDER BY relationLevel

结果：

RELATIONLEVEL LHID LOCATION PARENT 1 2 Trim - South Trim 2 3 South-1 Trim - South 2 4 South-2 Trim - South 3 4 South-2-1 South-2

DEMO

在层次结构SQL中查找所有子项

1 个答案: