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问题描述
我有两个表,一个包含节点,第二个包含它们之间的关系,如下所示:
I have two tables, one that contains nodes and second that contains the relationships between them like so:
表A(命名节点)
NodeID | NodeName
100 | Name 1
101 | Name 2
102 | Name 3
表 B(命名关系)
NodeParent | NodeChild
100 | 101
101 | 102
我需要执行一个查询,该查询需要找出哪些节点是孤立节点(它们不在关系表中).如何同时搜索 NodeParent 和 NodeChild?
I need to execute a query that needs to find which nodes are orphans (they are not in the Relationship table). How can I search through NodeParent and NodeChild at the same time?
推荐答案
SELECT
n.NodeID
FROM
Node AS n
LEFT JOIN
Relationship AS r
ON
n.NodeID = r.NodeChild
WHERE
r.NodeChild IS NULL
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