初始化SortOrder列（例如0,1,2,3）的最佳方法是什么，其中有多个组基于另一个字段？

Question

I have a table of list items. There is a ListID column used as an identifier to group the list items together. Is there a sane way to give every item a sort order, starting at 0 per list and incremental by one per item.

Basically, I need to populate the following SortOrder Column values for a large number of entries/ListIDs.

ID    ListID    SortOrder
1     1         0
2     0         0
3     1         1
4     0         1
5     1         2
6     0         2
7     2         0
8     2         1
9     2         2

Answer 1

You can use ROW_NUMBER() with a PARTITION on the ListId field for this:

Select   Id, ListId, 
         Row_Number() Over (Partition By ListId Order By Id) -1 As SortOrder
From     YourTable
Order By Id

Answer 2

I think you want:

WITH toupdate as (
      SELECT t.*,
             ROW_NUMBER() OVER (PARTITION BY ListId Order By id) as new_SortOrder
      FROM tableName
     )
UPDATE toupdate a
    SET sortorder = new_sort_order;

SQL Server has the nice ability to update a subquery or CTE under some circumstances.

Answer 3

Do you need to persist the order of lists containing items that are shared between lists? If so, perhaps variations on this schema would work for you.

Item
id    label
1     A
2     B
3     C
4     D

List
id    listName
1     abc list
2     cbd list
3     aaa list

ListMembership
id    listId   itemId   order
1     1        1        1
2     1        2        2
3     1        3        3
4     2        2        2
5     2        3        1
6     2        4        3
7     3        1        1
8     3        1        2
9     3        1        3

usage:

select i.label from listMembership as lm
   join Item as i on i.id=lm.itemId
   where lm.listId=2
   order by lm.order

yields:

label
C
B
D