顯示錶的人與SQL

Question

孫子我有一個名爲person(ID,fname,Age,Gender,parentID)， 誰能告訴如何顯示誰沒有盛大的兒童在SQL個人表？

Answer 1

這應該做的伎倆，但如果你有很多的人有很多孩子可能會有點慢：

SELECT DISTINCT p.* 
FROM person p 
LEFT JOIN person c ON c.parentID = p.ID 
LEFT JOIN person gc on gc.parentID = c.ID 
WHERE gc.ID IS NULL 

Answer 2

SELECT * 
FROM person 
WHERE 
ID NOT IN (
      SELECT id 
      FROM (
       SELECT p.*,c.id as childID,g.id AS grandChildId 
       FROM person p 
       LEFT JOIN person c 
       ON c.parentID = p.ID 
       LEFT JOIN person g 
       ON g.parentID = c.ID 
       ) AS person_relation 
      WHERE grandChildId 
      is NOT NULL 

創建臨時表可以是有益的，但對於單個查詢這將工作。