SQL Server显示视图以在父级和子级显示产品 我有一张这样的桌子：

我希望有一个横向表示用于报告，例如：

+----+---------+---------+----------+
| ID |  Name   | level1  |  level2  |
+----+---------+---------+----------+
|  4 | T-shirt | Clothes | Null     |
|  5 | skirt   | Clothes | Null     |
|  6 | pizza   | Food    | fastfood |
|  7 | snack   | Food    | fastfood |
+----+---------+---------+----------+

---

有人知道怎么做吗？

您可以使用两级

左连接：

select t.*,
       coalesce(tpp.name, tp.name) as level1,
       (case when tpp.name is not null then tp.name end) as level2
from t left join
     t tp
     on t.parent_id = tp.id left join
     t tpp
     on tp.parent_id = tpp.parent_id
where not exists (select 1
                  from t tc
                  where tc.parent_id = t.id);

我试过了，但没用。我也使用left连接表格，但结果是：ID--Name--level1--level2 4 T恤衣服空5裙子衣服空6比萨快餐7零食快餐我想表明level1是最高的家长level@AnnYoah . . . 我修改了答案，使值的顺序相反。
select t.*,
       coalesce(tpp.name, tp.name) as level1,
       (case when tpp.name is not null then tp.name end) as level2
from t left join
     t tp
     on t.parent_id = tp.id left join
     t tpp
     on tp.parent_id = tpp.parent_id
where not exists (select 1
                  from t tc
                  where tc.parent_id = t.id);