MySQL은 - 나는 두 개의 테이블이 바로 테이블

Question

에서에서 조인 행에 조건 : 지금은 foreign_id 열 orders와 activities에 가입해야

mysql> select * from orders; 
+------+---------------------+------------+---------+ 
| id | created_at   | foreign_id | data | 
+------+---------------------+------------+---------+ 
| 1 | 2010-10-10 10:10:10 |   3 | order 1 | 
| 4 | 2010-10-10 00:00:00 |   6 | order 4 | 
| 5 | 2010-10-10 00:00:00 |   7 | order 5 | 
+------+---------------------+------------+---------+ 

mysql> select * from activities; 
+------+---------------------+------------+------+ 
| id | created_at   | foreign_id | verb | 
+------+---------------------+------------+------+ 
| 1 | 2010-10-10 10:10:10 |   3 | get | 
| 2 | 2010-10-10 10:10:15 |   3 | set | 
| 3 | 2010-10-10 10:10:20 |   3 | put | 
| 4 | 2010-10-10 00:00:00 |   6 | get | 
| 5 | 2010-10-11 00:00:00 |   6 | set | 
| 6 | 2010-10-12 00:00:00 |   6 | put | 
+------+---------------------+------------+------+ 

을 : 모든 주문 등을 위해 (있는 경우) 하나의 작업을 선택 ABS(TIMESTAMPDIFF(SECOND, orders.created_at, activities.created_at))은 최소입니다. 예 : 순서와 활동은 거의 동시에 생성되었습니다.

+----------+---------+---------------------+-------------+------+---------------------+ 
| order_id | data | order_created_at | activity_id | verb | activity_created_at | 
+----------+---------+---------------------+-------------+------+---------------------+ 
|  1 | order 1 | 2010-10-10 10:10:10 |   1 | get | 2010-10-10 10:10:10 | 
|  4 | order 4 | 2010-10-10 00:00:00 |   4 | get | 2010-10-10 00:00:00 | 
|  5 | order 5 | 2010-10-10 00:00:00 |  NULL | NULL | NULL    | 
+----------+---------+---------------------+-------------+------+---------------------+ 

다음 쿼리는 원하는 행을 포함하는 행 집합을 생성합니다. GROUP BY 문이 포함 된 경우 activities의 행을 제어 할 수 없습니다.

SELECT o.id AS order_id 
    , o.data AS data 
    , o.created_at AS order_created_at 
    , a.id AS activity_id 
    , a.verb AS verb 
    , a.created_at AS activity_created_at 
FROM orders AS o 
LEFT JOIN activities AS a ON a.foreign_id = o.foreign_id; 

이러한 쿼리를 작성할 수 있습니까? 이상적으로 나는이 섹션이 더 큰보고 질투의 일부이기 때문에 group by을 사용하지 않는 것이 좋습니다. 당신이 원하는 무엇을

Answer 1

두 테이블이 어떤 신비 외래 키를 참조하기 때문에이 아래 쿼리 오류 가능성,하지만 그것은 당신에게 당신이 당신의 목적을 위해 적용 할 수있는 원리를 제공 할 수 있습니다 ...

DROP TABLE IF EXISTS orders; 

CREATE TABLE orders 
(id INT NOT NULL PRIMARY KEY 
,created_at DATETIME NOT NULL 
,foreign_id INT NOT NULL 
,data VARCHAR(20) NOT NULL 
); 

INSERT INTO orders VALUES 
(1 ,'2010-10-10 10:10:10',3 ,'order 1'), 
(4 ,'2010-10-10 00:00:00',6 ,'order 4'), 
(5 ,'2010-10-10 00:00:00',7 ,'order 5'); 

DROP TABLE IF EXISTS activities; 

CREATE TABLE activities 
(id INT NOT NULL AUTO_INCREMENT PRIMARY KEY 
,created_at   DATETIME NOT NULL 
,foreign_id INT NOT NULL 
,verb VARCHAR(20) NOT NULL 
); 

INSERT INTO activities VALUES 
(1,'2010-10-10 10:10:10',3,'get'), 
(2,'2010-10-10 10:10:15',3,'set'), 
(3,'2010-10-10 10:10:20',3,'put'), 
(4,'2010-10-10 00:00:00',6,'get'), 
(5,'2010-10-11 00:00:00',6,'set'), 
(6,'2010-10-12 00:00:00',6,'put'); 

SELECT o.id order_id 
    , o.data 
    , o.created_at order_created_at  
    , a.id activity_id 
    , a.verb 
    , a.created_at activity_created_at 
    FROM activities a 
    JOIN orders o 
    ON o.foreign_id = a.foreign_id 
    JOIN 
    (SELECT a.foreign_id 
      , MIN(ABS(TIMEDIFF(a.created_at,o.created_at))) x 
     FROM activities a 
     JOIN orders o 
      ON o.foreign_id = a.foreign_id 
     GROUP 
      BY a.foreign_id 
    ) m 
    ON m.foreign_id = a.foreign_id 
    AND m.x = ABS(TIMEDIFF(a.created_at,o.created_at)) 
UNION DISTINCT 
SELECT o.id 
    , o.data 
    , o.created_at 
    , a.id 
    , a.verb 
    , a.created_at 
    FROM orders o 
    LEFT 
    JOIN activities a 
    ON a.foreign_id = o.foreign_id 
WHERE a.foreign_id IS NULL; 
; 

+----------+---------+---------------------+-------------+------+---------------------+ 
| order_id | data | order_created_at | activity_id | verb | activity_created_at | 
+----------+---------+---------------------+-------------+------+---------------------+ 
|  1 | order 1 | 2010-10-10 10:10:10 |   1 | get | 2010-10-10 10:10:10 | 
|  4 | order 4 | 2010-10-10 00:00:00 |   4 | get | 2010-10-10 00:00:00 | 
|  5 | order 5 | 2010-10-10 00:00:00 |  NULL | NULL | NULL    | 
+----------+---------+---------------------+-------------+------+---------------------+