Question

假设我有以下表格：

CREATE TABLE parents (
    id int primary key
);

CREATE TABLE children (
    parent_id int,  --id from parents
    day int,
    status bool,
}

INSERT INTO parents (id) VALUES (1);
INSERT INTO children (parent_id, day, status) VALUES (1, 1, TRUE);
INSERT INTO children (parent_id, day, status) VALUES (1, 2, TRUE);

INSERT INTO parents (id) VALUES (2);
INSERT INTO children (parent_id, day, status) VALUES (2, 1, TRUE);
INSERT INTO children (parent_id, day, status) VALUES (2, 2, FALSE);

INSERT INTO parents (id) VALUES (3);
INSERT INTO children (parent_id, day, status) VALUES (3, 1, TRUE); 

INSERT INTO parents (id) VALUES (4);
INSERT INTO children (parent_id, day, status) VALUES (4, 1, FALSE);

INSERT INTO parents (id) VALUES (5);

我需要一个将返回的查询：

Parents
+------------+
|    id      |
+------------+
|     1      |
|     3      |
+------------+

其中id是父母ID。结果表仅包含始终（任何一天）true的父项。请注意，应排除没有孩子的父母。

我的尝试：

SELECT id
FROM parents p
INNER JOIN children c ON c.parent_id=p.id
WHERE c.status = TRUE
GROUP BY id

但它也会给父母id=2。

另一次尝试：

SELECT id
FROM parents p
LEFT OUTER JOIN children c ON c.parent_id=p.id AND c.status=FALSE
WHERE c.status IS NULL
GROUP BY id

但是这种方法还包括id=5的父级，必须将其排除在外。

Answer 1

您不需要加入父母。

SELECT parent_id
FROM children
GROUP BY parent_id
HAVING MIN(Status) = 'TRUE'
   AND MAX(Status) = 'TRUE'

除了TRUE之外没有其他状态。

Answer 2

SELECT id FROM parent P 
WHERE (P.id) IN
(SELECT c.parent_id FROM children c WHERE c.status = TRUE)

这将为您提供所需的结果。

Answer 3

这可能也有效

SELECT DISTINCT p.id
  FROM parents p
 WHERE p.id IN ( 
                 SELECT c.parent_id
                   FROM children c
                  WHERE c.status = TRUE
                    AND c.parent_id = p.id 
               )

Answer 4

使用bit_add：

select a.id
from parents a
join children b on a.id = b.parent_id
group by a.id
having bit_and(b.status);

sqlfiddle

选择连接表中的字段在每行中相同的行

4 个答案: