postgresql – 使用Query递归查找父
发布时间:2020-12-13 16:28:57 所属栏目:百科 来源:网络整理
导读:我正在使用postgresql.我的桌子如下所示 parent_id child_id----------------------101 102103 104104 105105 106 我想写一个sql查询,它将给出输入的最终父级. 假设我以106作为输入,则其输出为103. (106 -- 105 -- 104 -- 103) 这是一个完整的例子.首先是DDL
我正在使用postgresql.我的桌子如下所示 parent_id child_id ---------------------- 101 102 103 104 104 105 105 106 我想写一个sql查询,它将给出输入的最终父级. 假设我以106作为输入,则其输出为103. (106 --> 105 --> 104 --> 103)
这是一个完整的例子.首先是DDL:
test=> CREATE TABLE node ( test(> id SERIAL,test(> label TEXT NOT NULL,-- name of the node test(> parent_id INT,test(> PRIMARY KEY(id) test(> ); NOTICE: CREATE TABLE will create implicit sequence "node_id_seq" for serial column "node.id" NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "node_pkey" for table "node" CREATE TABLE …和一些数据… test=> INSERT INTO node (label,parent_id) VALUES ('n1',NULL),('n2',1),('n3',2),('n4',3); INSERT 0 4 test=> INSERT INTO node (label) VALUES ('garbage1'),('garbage2'),('garbage3'); INSERT 0 3 test=> INSERT INTO node (label,parent_id) VALUES ('garbage4',6); INSERT 0 1 test=> SELECT * FROM node; id | label | parent_id ----+----------+----------- 1 | n1 | 2 | n2 | 1 3 | n3 | 2 4 | n4 | 3 5 | garbage1 | 6 | garbage2 | 7 | garbage3 | 8 | garbage4 | 6 (8 rows) 这对节点中的每个id执行递归查询: test=> WITH RECURSIVE nodes_cte(id,label,parent_id,depth,path) AS ( SELECT tn.id,tn.label,tn.parent_id,1::INT AS depth,tn.id::TEXT AS path FROM node AS tn WHERE tn.parent_id IS NULL UNION ALL SELECT c.id,c.label,c.parent_id,p.depth + 1 AS depth,(p.path || '->' || c.id::TEXT) FROM nodes_cte AS p,node AS c WHERE c.parent_id = p.id ) SELECT * FROM nodes_cte AS n ORDER BY n.id ASC; id | label | parent_id | depth | path ----+----------+-----------+-------+------------ 1 | n1 | | 1 | 1 2 | n2 | 1 | 2 | 1->2 3 | n3 | 2 | 3 | 1->2->3 4 | n4 | 3 | 4 | 1->2->3->4 5 | garbage1 | | 1 | 5 6 | garbage2 | | 1 | 6 7 | garbage3 | | 1 | 7 8 | garbage4 | 6 | 2 | 6->8 (8 rows) 这得到所有后代WHERE node.id = 1: test=> WITH RECURSIVE nodes_cte(id,tn.id::TEXT AS path FROM node AS tn WHERE tn.id = 1 UNION ALL SELECT c.id,(p.path || '->' || c.id::TEXT) FROM nodes_cte AS p,node AS c WHERE c.parent_id = p.id ) SELECT * FROM nodes_cte AS n; id | label | parent_id | depth | path ----+-------+-----------+-------+------------ 1 | n1 | | 1 | 1 2 | n2 | 1 | 2 | 1->2 3 | n3 | 2 | 3 | 1->2->3 4 | n4 | 3 | 4 | 1->2->3->4 (4 rows) 以下将获取节点的ID为4的路径: test=> WITH RECURSIVE nodes_cte(id,node AS c WHERE c.parent_id = p.id ) SELECT * FROM nodes_cte AS n WHERE n.id = 4; id | label | parent_id | depth | path ----+-------+-----------+-------+------------ 4 | n4 | 3 | 4 | 1->2->3->4 (1 row) 让我们假设你想限制搜索到深度小于3的后代(请注意,深度还没有增加): test=> WITH RECURSIVE nodes_cte(id,path) AS ( SELECT tn.id,tn.id::TEXT AS path FROM node AS tn WHERE tn.id = 1 UNION ALL SELECT c.id,(p.path || '->' || c.id::TEXT) FROM nodes_cte AS p,node AS c WHERE c.parent_id = p.id AND p.depth < 2 ) SELECT * FROM nodes_cte AS n; id | label | parent_id | depth | path ----+-------+-----------+-------+------ 1 | n1 | | 1 | 1 2 | n2 | 1 | 2 | 1->2 (2 rows) 我建议使用ARRAY数据类型而不是用于演示“路径”的字符串,但箭头更多地说明了父< =>子关系. (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |
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