sql server图形查询，找到节点的所有路径

Question

我有一个非常常见的问题，我试图使用图形查询来解决（sql server 2017）。

1. 我想构建一个查询并查找节点中的任何人如何连接到C.
2. 我想构建一个查询并查找节点中的任何人如何连接C（有 1 或 2 个连接）。

这是创建该图的完整脚本：

DROP TABLE IF EXISTS Person;
CREATE TABLE Person (userName VARCHAR(100)  PRIMARY KEY) AS NODE;

INSERT INTO Person (userName) VALUES ('A'),('B'),('C'),('D'),('E'),('F'); 

DROP TABLE IF EXISTS Follow; 
CREATE TABLE Follow AS EDGE;

INSERT INTO Follow ($from_id, $to_id) VALUES (
   (SELECT $node_id FROM dbo.Person WHERE userName = 'A'),
   (SELECT $node_id FROM dbo.Person WHERE userName = 'E')),

   ((SELECT $node_id FROM dbo.Person WHERE userName = 'E'),
   (SELECT $node_id FROM dbo.Person WHERE userName = 'C')),


   ((SELECT $node_id FROM dbo.Person WHERE userName = 'C'),
   (SELECT $node_id FROM dbo.Person WHERE userName = 'A')),


   ((SELECT $node_id FROM dbo.Person WHERE userName = 'A'),
   (SELECT $node_id FROM dbo.Person WHERE userName = 'F')),

   ((SELECT $node_id FROM dbo.Person WHERE userName = 'F'),
   (SELECT $node_id FROM dbo.Person WHERE userName = 'B')),

   ((SELECT $node_id FROM dbo.Person WHERE userName = 'B'),
   (SELECT $node_id FROM dbo.Person WHERE userName = 'F')),

   ((SELECT $node_id FROM dbo.Person WHERE userName = 'B'),
   (SELECT $node_id FROM dbo.Person WHERE userName = 'E')),

   ((SELECT $node_id FROM dbo.Person WHERE userName = 'E'),
   (SELECT $node_id FROM dbo.Person WHERE userName = 'B'));

这个查询不起作用，因为它只给我直接关系：

SELECT Person1.userName as userName1, Person2.userName as userName2   
FROM Person as Person1, Follow, Person as Person2 
WHERE MATCH(Person1-(Follow)->Person2)
AND Person2.userName = 'C'

Answer 1

你可以尝试如下所示：

SELECT 
        p1.userName, 
        p1.userName as StartNode,
        LAST_VALUE(p2.userName) WITHIN GROUP (GRAPH PATH) AS FinalNode,
        STRING_AGG(p2.userName,'->') WITHIN GROUP (GRAPH PATH) AS [Edges Path],
        COUNT(p2.userName) WITHIN GROUP (GRAPH PATH) AS Levels
    FROM
        dbo.Person p1,
        dbo.Person FOR PATH p2,
        dbo.Follow FOR PATH Follow
    WHERE 
        MATCH(SHORTEST_PATH(p1(-(Follow)->p2)+))
        AND p1.userName = 'C';

要查找节点的所有传入连接，我们需要包装最终节点的查询和过滤器，如下所示：

SELECT
    username, StartNode, [Edges Path], FinalNode, Levels
FROM (
    SELECT 
        P1.username, 
        P1.username as StartNode, 
        STRING_AGG(P2.userName,'->') WITHIN GROUP (GRAPH PATH) AS [Edges Path],
        LAST_VALUE(P2.userName) WITHIN GROUP (GRAPH PATH) AS FinalNode,
        COUNT(P2.userName) WITHIN GROUP (GRAPH PATH) AS Levels
    FROM
        Person P1,
        Person FOR PATH P2,
        Follow FOR PATH Follow
    WHERE 
        MATCH(SHORTEST_PATH(P1(-(Follow)->P2)))
 ) AS Q
 WHERE Q.FinalNode = 'C'

为了限制级别或跳数，我们可以提供递归量词来代替 (+ --- 一个或多个)，如下所示：

SELECT
    username, StartNode, [Edges Path], FinalNode, Levels
FROM (
    SELECT 
        P1.username, 
        P1.username as StartNode, 
        STRING_AGG(P2.userName,'->') WITHIN GROUP (GRAPH PATH) AS [Edges Path],
        LAST_VALUE(P2.userName) WITHIN GROUP (GRAPH PATH) AS FinalNode,
        COUNT(P2.userName) WITHIN GROUP (GRAPH PATH) AS Levels
    FROM
        Person P1,
        Person FOR PATH P2,
        Follow FOR PATH Follow
    WHERE 
        MATCH(SHORTEST_PATH(P1(-(Follow)->P2){1,3}))
 ) AS Q
 WHERE Q.FinalNode = 'C'