Sql server 查询中每个字段的位置值

在我提出关于（分层数据的反向查询）的问题之前

我得到了90%的答案

select i.ID, l.lev1 as Name, NULL as Parent
from IDTable i 
 join LevelTable l on i.Name = l.lev1
 union
select i.ID, l.lev2 as Name, (select j.ID from IDTable j where j.Name = l.lev1)
from IDTable i 
 join LevelTable l on i.Name = l.lev2
 union
select i.ID, l.lev3 as Name, (select j.ID from IDTable j where j.Name = l.lev2)
from IDTable i 
 join LevelTable l on i.Name = l.lev3

现在为了完全得到我的答案，我还有一个问题

我如何在我的查询中获得每个字段的位置。例如，管、LCD、等离子电视的父项现在我需要位置字段值，根据字母顺序给出每个位置的值（0、1、2、3…）

category_id   | name                   | parent |position

 +-------------+----------------------+--------+-------
|           1 | ELECTRONICS          |   NULL |0
|           2 | TELEVISIONS          |      1 |0
|           3 | TUBE                 |      2 |3
|           4 | LCD                  |      2 |1
|           5 | PLASMA               |      2 |2

---

您应该能够将row_number（）函数与分区一起使用

select *, row_number() over (partition by parent order by name) as position from (
    select i.ID, l.lev1 as Name, NULL as Parent
    from IDTable i 
     join LevelTable l on i.Name = l.lev1
     union
    select i.ID, l.lev2 as Name, (select j.ID from IDTable j where j.Name = l.lev1)
    from IDTable i 
     join LevelTable l on i.Name = l.lev2
     union
    select i.ID, l.lev3 as Name, (select j.ID from IDTable j where j.Name = l.lev2)
    from IDTable i 
     join LevelTable l on i.Name = l.lev3
) as q