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Question

我不知道这是否是可能的，但我想我可以问

我有家庭和亚科（family_table）的表：

family_id family_name  parent_id 
1   Family 1  null 
2   Family 2  null 
3   Subfamily 1.1 1 
4   Subfamily 1.2 1 
5   Family 3  null 
6   Subfamily 2.1 2 

然后，我有一个复杂的选择返回一些family_id，如2，4

那我就需要返回以下信息：

principal_id family_name  subfamily_id subfamily_name 
2    Family 2  null   null 
1    Family 1  4    Subfamily 1.2 

编辑：我不介意改变如何显示结果或改变别的东西，只要它足够清楚。

这是我到目前为止已经完成：

SELECT 
    CASE 
WHEN ft.parent_id IS NULL THEN 
    ft.family_id 
ELSE 
    ft.parent_id 
END AS principal_id, 
/*I was thinking something like this, but I don't know how to select another row value here, or if there would be another way 
CASE 
WHEN ft.parent_id IS NULL THEN 
    ft.family_name 
ELSE 
    *Family name from the parent* 
END AS family_name*/ 
FROM 
    family_table ft 
LEFT JOIN family_table ft2 ON ft2.parent_id = ft.family_id 
WHERE 
    ft.family_id IN (2,4/*complicated select*/) 

编辑：此尝试BELOW是行不通的，因为它把结果返回从亚科作为一个家庭，它不加入我需要的子系列的父母ID。

或者，也许是这样的：

SELECT 
    ft.family_id as principal_id, 
    ft.family_name as family_name, 
    ft2.family_id as subfamily_id, 
    ft2.family_name as subfamily_name 
FROM ft.family_table 
LEFT JOIN ft2.family_table ON ft2.parent_id = ft.family_id 
WHERE 
    /*ft.family_id OR ft2.parent_id*/ IN (2,4/*complicated select*/) 

我不想做ft.family_id IN (2,4/*complicated select*/) OR cf2.parent_id IN (2,4/*complicated select*/)重复滔天的选择。 我有我过于复杂一切的感觉......

---

这最终的查询，以接受的答案进去（万一有人不知道）

SELECT 
    COALESCE (ft2.family_id, ft.family_id) AS family_id, 
    COALESCE (ft2.family_name, ft.family_name) AS family_name, 
    CASE WHEN ft.parent_id IS NOT NULL THEN ft.family_id 
    END AS subfamily_id, 
    CASE WHEN ft.parent_id IS NOT NULL THEN ft.family_name 
    END AS subfamily_name 
FROM family_table ft 
JOIN (/* complicated select */) AS t ON t.family_id IN (ft.family_id, ft.parent_id) 
LEFT JOIN family_table ft2 ON ft2.family_id = ft.parent_id 

Answer 1

尝试加入到“复杂的选择”，而不是使用IN()，这样的事情：

SELECT 
..... 
FROM 
    family_table ft 
LEFT JOIN family_table ft2 ON ft2.parent_id = ft.family_id 
JOIN (/* complicated select here */) t 
ON(t.ID_OR_WHATEVER IN(ft.family_id,cf2.parent_id)) 

这会有同样的效果。