MySQL如何找到確切的兒童組父母？

Question

的MySQL 5.5

 
parent table: 
id | facts 

 
child table: 
parent_id | foreign_key | facts 

現在，我想找到具有一定的確切集合的孩子，沒有更多，不會少的父母。像這樣：

SELECT t1.`id` 
from `parent_table` t1 
    LEFT JOIN `child_table` t2 ON t1.id=t2.parent_id 
WHERE t2.`fk` = 1 
    AND t2.`fk` = 3 
    AND t2.`fk` = 5 
    AND t2.`fk` = 7 
    AND t2.`fk` = 9 

但是，這也將得到一個父記錄與這組兒童：1,2,3,5,7,9。我只想要那些有確切集合的父母：1,3,5,7,9。

有沒有辦法？

編輯： child.parent_id和child.fk是都不是唯一的。 child.fk是連接到另一個表的外鍵。 （「多對多關係」）因此，父母有可能生孩子1,2,3,5,7,9。我做這個查詢的全部原因是爲了避免爲1,3,5,7,9創建一個新的父項，如果這樣的父項已經存在的話。

Answer 1

假設child.id對於每個child.parent_id都是唯一的。

SELECT a.id, a.facts 
FROM parent a 
     INNER JOIN child b 
      ON a.id = b.parent_ID 
WHERE b.id IN (1,3,5,7,9) AND  -- <<== list all ChildID here 
     EXISTS       -- <<== this part checks if the parent_ID 
     (        --   present on the EXISTS clause 
      SELECT parent_ID   --   which only filters parents 
      FROM child c   --   with 5 children 
      WHERE b.parent_ID = c.parent_ID 
      GROUP BY parent_ID 
      HAVING COUNT(*) = 5  -- <<== total number of children 
     ) 
GROUP BY a.id, a.facts 
HAVING COUNT(*) = 5     -- <<== total number of children 

• SQLFiddle Demo (more info included)

Answer 2

SELECT parent_id 
FROM  child_table 
GROUP BY parent_id 
HAVING SUM(id IN (1,3,5,7,9)) = COUNT(*) 
    AND COUNT(DISTINCT id) = 5 

Answer 3

這個問題被稱爲（精確）關係分裂。本文中有很多有用的代碼和解釋：Divided We Stand: The SQL of Relational Division。

一種方法來解決這個問題：

SELECT p.id AS parent_id 
FROM parent AS p 
WHERE EXISTS 
     (SELECT * FROM child AS c 
     WHERE c.fk = 1 AND c.parent_id = p.id) 
    AND EXISTS 
     (SELECT * FROM child AS c 
     WHERE c.fk = 3 AND c.parent_id = p.id) 
    AND EXISTS 
     (SELECT * FROM child AS c 
     WHERE c.fk = 5 AND c.parent_id = p.id) 
    AND EXISTS 
     (SELECT * FROM child AS c 
     WHERE c.fk = 7 AND c.parent_id = p.id) 
    AND EXISTS 
     (SELECT * FROM child AS c 
     WHERE c.fk = 9 AND c.parent_id = p.id) 
    AND NOT EXISTS 
     (SELECT * FROM child AS c 
     WHERE c.fk NOT IN (1,3,5,7,9) AND c.parent_id = p.id) ; 

而在StackOverflow上，另一個鏈接到一個類似的問題，在這裏，你會發現超過10級不同的解決方案（注：這是不是確切的劃分，但對於與餘數師）和性能測試（Postgres的）：How to filter SQL results in a has-many-through relation

Answer 4

類似eggyal的解決方案，只是想我會在把它作爲一種替代，因爲它應該是更輕便跨RDBMS的;

SELECT c.parent_id 
FROM child_table c 
GROUP BY c.parent_id 
HAVING SUM(CASE WHEN c.id IN (1,3,5,7,9) THEN 1 ELSE -1 END) = 5 

5是你想匹配IN子句中的孩子的確切數量（在這種情況下，所有）

這將僅具有鮮明的孩子工作，如果有重複，這將打破。

An SQLfiddle to test with。