java - tree形结构的Nested Set 数据如何转成Adjacency List的

Answer 1

I thought it was simple before and needed one more layer of subqueries. The modification is as follows:

SELECT node.name, parent.id AS pid
FROM `nested` as node
  LEFT OUTER JOIN `nested` AS parent
    ON parent.`left` = (
      SELECT MAX(parents.`left`)
      FROM nested AS parents
      WHERE node.`left` > parents.`left` AND node.`left` < parents.`right`
    )
ORDER BY node.id;

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Refer to the second example in the "Getting the Whole Tree" section of https://segmentfault.com/a/11... that I translated and compiled before. The main modification is to change (COUNT(parent.name) - 1) AS depth 改成 parent.id to get a form similar to the adjacency list. .