PostgreSQL中的递归查询。选择 *

Question

我有递归查询来检索给定人的所有孩子

WITH RECURSIVE recursetree(id, parent_id) AS (
    SELECT id, parent_id FROM tree WHERE parent_id = 0
  UNION
    SELECT t.id, t.parent_id
    FROM tree t
    JOIN recursetree rt ON rt.id = t.parent_id
  )
SELECT * FROM recursetree;

如您所见，我正在指定要检索的列的列表。但是我想使用SELECT *（实际表中确实有很多列，以后可以更改它们）。有没有某种方法可以获取ALL列而不单独定义每个列？

Answer 1

您不需要在WITH部件中指定列。如果您忽略这一点，列名将由 中的第一个查询确定UNION：

WITH RECURSIVE recursetree AS (
    SELECT * FROM tree WHERE parent_id = 0
  UNION
    SELECT t.*
    FROM tree t
    JOIN recursetree rt ON rt.id = t.parent_id
)
SELECT * 
FROM recursetree;

Answer 2

快速破解（重新加入原版）：

WITH RECURSIVE recursetree(id, parent_id) AS (
    SELECT id, parent_id FROM tree WHERE parent_id = 0
  UNION
    SELECT t.id, t.parent_id
    FROM tree t
    JOIN recursetree rt ON rt.id = t.parent_id
  )
SELECT *
FROM tree tr
WHERE EXISTS ( SELECT 1
    FROM recursetree x
    WHERE x.id = tr.id
    );