sqlite - 选择特定值 SQLite

Question

我有一个问题，我正在使用 sqlite，

首先我创建了一个表:

 CREATE TABLE tree(
     id_tree integer PRIMARY KEY AUTOINCREMENT,
     id_boss TEXT,
     id_child TEXT,
     answ TEXT);

插入一些值:

 INSERT INTO tree(id_boss,id_child,answ) VALUES('1','8','T');
 INSERT INTO tree(id_boss,id_child,answ) VALUES('1',null,'F');
 INSERT INTO tree(id_boss,id_child,answ) VALUES('8','P1','T');
 INSERT INTO tree(id_boss,id_child,answ) VALUES('8','2','F');
 INSERT INTO tree(id_boss,id_child,answ) VALUES('2','P2','T');
 INSERT INTO tree(id_boss,id_child,answ) VALUES('2','P3','F');

并执行查询:

 WITH RECURSIVE
 ancestor(id) AS (
  VALUES('P3')
  UNION ALL
  SELECT tree.id_boss
  FROM tree JOIN ancestor ON tree.id_child = ancestor.id
  )
 SELECT id FROM ancestor;

结果是:

  P3
  2
  8
  1

我的问题是，如何进行查询以选择“T”值中的 id_boss 并忽略“F”中的所有值？

结果应该是这样的:

  P3
  1

Answer 1

您无法从 CTE 内部过滤掉 F 记录，因为这会破坏树中的连接。相反，您必须返回 answ 值，并在第二步中将它们用作过滤器:

WITH RECURSIVE
ancestors(id, answ) AS (
  VALUES('P3', 'T')
  UNION ALL
  SELECT tree.id_boss, tree.answ
  FROM tree JOIN ancestors ON tree.id_child = ancestors.id
)
SELECT id FROM ancestors WHERE answ = 'T';