Question

我有一张如下表：

Rel_Id  Last    First   Relation
1   Jones   John    Primary
1   Jones   Mary    Spouse
1   Jones   Carl    Dependent
2   Will    Bill    Primary
3   Fine    Howard  Primary
4   Smith   Diana   Primary
4   Smith   Axel    Spouse

我正在尝试返回所有“主要”关系，每行一个，但如果有一个，请将Spouse包含在同一行中。

我想要达到的结果如下：

1   Jones   John    Primary Jones   Mary    Spouse
2   Will    Bill    Primary null    null    null
3   Fine    Howard  Primary null    null    null
4   Smith   Diana   Primary Smith   Axel    Spouse

或者这也没关系：

1   Jones   John    Primary Jones   Mary    Spouse
2   Will    Bill    Primary Will    Bill    Primary
3   Fine    Howard  Primary Fine    Howard  Primary
4   Smith   Diana   Primary Smith   Axel    Spouse

这是我的疑问：

SELECT
P.Rel_Id,
P.Last,
P.`First`,
P.Relation,
S.Last AS sLast,
S.`First` AS sFirst,
S.Relation AS sRelation
FROM
relations AS P
LEFT JOIN relations AS S ON S.Rel_Id = P.Rel_Id
WHERE P.Relation = 'Primary' 
AND S.Relation <> 'Dependent'

以上查询结果为：

1   Jones   John    Primary Jones   John    Primary
1   Jones   John    Primary Jones   Mary    Spouse
2   Will    Bill    Primary Will    Bill    Primary
3   Fine    Howard  Primary Fine    Howard  Primary
4   Smith   Diana   Primary Smith   Diana   Primary
4   Smith   Diana   Primary Smith   Axel    Spouse

不幸的是，我的查询在正确排除'Dependent'的情况下显示了两行，其中有一个独特的'Primary'成员，其中有一个Spouse，我不想要。如果每个'Primary'关系只返回一行，只有一个Spouse如果还有一个吗？

Answer 1

您需要在连接条件中在查询中添加其他检查，以便不显示两个Primary，并且仅显示配偶。

因此，在查询中添加此条件：

S.Relation <> P.Relation

所以最终的查询将成为：

SELECT
P.Rel_Id,
P.Last,
P.`First`,
P.Relation,
S.Last AS sLast,
S.`First` AS sFirst,
S.Relation AS sRelation
FROM
relations AS P
LEFT JOIN relations AS S ON S.Rel_Id = P.Rel_Id AND S.Relation <> P.Relation
WHERE P.Relation = 'Primary' 
AND S.Relation <> 'Dependent'

希望这有帮助。

Answer 2

SELECT  GROUP_CONCAT(CONCAT_WS(' ',
                               last, first, relation),
                     SEPARATOR ' -- '
                     ORDER BY IF(relation = 'PRIMARY', 0, rel_id)
        ) AS Family
    FROM relations
    GROUP BY last;

它没有给你＆＃34;列＆＃34;就像你要求的那样，但它可能会这样做。

这将处理任何人数的家庭。但是，它取决于last是唯一的。（这是架构设计中存在的一个缺陷。）

将last分开可能会更好：

SELECT  last,
        GROUP_CONCAT(CONCAT_WS(' ',
                               first, relation),
                     SEPARATOR ' -- '
                     ORDER BY IF(relation = 'PRIMARY', 0, rel_id)
        ) AS Family
    FROM relations
    GROUP BY last;

Answer 3

现在看起来很明显 - 而且很简单！（非常感谢 - 真的）

SELECT
P.Rel_Id,
P.Last,
P.`First`,
P.Relation,
S.Rel_Id AS sRel_Id,
S.Last AS sLast,
S.`First` AS sFirst,
S.Relation AS sRelation
FROM
relations AS P
LEFT JOIN relations AS S ON S.Rel_Id = P.Rel_Id and S.Relation = 'Spouse'
WHERE P.Relation = 'Primary'

Left Self Join每个'primary'返回一行

3 个答案: