SQL 查询根据另一列中的最大值更新记录

Question

The Problem

I have this table. (You can also view it in DBFiddle .)

Id	Version	Item No.	Notes
1	NULL	31
2	1	31	tasty
3	2	31	kinda tasty
4	NULL	32
5	1	32	meh
6	2	32	alright
7	3	32	fabulous
8	NULL	33	ambivalent
9	1	33	gross
10	2	33	puke

The 1st column is the primary key. The 2nd and 3rd column are integers. The 4th column is a VARCHAR.

For every unique Item No. where its Version is NULL, I want to look at the record with the highest Version value, take the content of its Notes field, and copy it over.

This is much easier to understand visually; after the command is run, the table should look like this:

Id	Version	Item No.	Notes
1	NULL	31	kinda tasty
2	1	31	tasty
3	2	31	kinda tasty
4	NULL	32	fabulous
5	1	32	meh
6	2	32	alright
7	3	32	fabulous
8	NULL	33	ambivalent
9	1	33	gross
10	2	33	puke

Explanation of the Changes

• for Item No. 31, "kinda tasty" was copied over because it's in the record with the highest Version number, and the target cell is not occupied.
• for Item No. 32, "fabulous" was copied over for the same reason.
• "puke" was NOT copied over to replace "ambivalent", because the target cell is occupied.

The Question

What is the query to achieve this in SQL Server?

I know that I need a way of grouping records together by Item No. , find the one with the highest Version value, take its Notes value, and copy it to the record where the Version is NULL, but I am having trouble translating this to SQL.

Answer 1

Try this:

UPDATE t SET notes = (
   SELECT TOP 1 s.notes 
   FROM t s 
   WHERE s.item_no = t.item_no 
   ORDER BY version DESC
) WHERE version IS NULL AND notes IS NULL

Check demo

Answer 2

Use an updatable CTE:

WITH cte AS (
  SELECT *, FIRST_VALUE(Notes) OVER (PARTITION BY ItemNo ORDER BY Version DESC) newNotes 
  FROM tablename
)
UPDATE cte
SET Notes = newNotes
WHERE Version IS NULL AND Notes IS NULL;

See the demo .

Answer 3

Create a CTE to determine the value we need to update to, and then join that to your original table with update join syntax:

with maxVal as
(
    select row_number() over (partition by [Item No.] order by Version desc) rn
        , notes
        , [Item No.]
    from TestTable
    where Version is not null
)
update TestTable
set Notes = maxVal.Notes
from TestTable
left join maxVal
    on TestTable.[Item No.] = maxVal.[Item No.]
    and maxVal.rn = 1
where TestTable.Version is null
    and TestTable.Notes = ''

Answer 4

You can try this approach:

-- Preparing a table variable
DECLARE @table1 AS TABLE (
    id  INT IDENTITY(1,1) NOT NULL,
    VersionID INT,
    ItemNo INT,
    Note Varchar(50)
)

insert into 
    @table1 (VersionID,ItemNo,Note)
values 
    (NULL,31,''),
    (1,31,'tasty'),
    (2,31,'kinda tasty'),
    (NULL,32,''),
    (1,32,'meh'),
    (2,32,'alright'),
    (3,32,'fabulous'),
    (NULL,33,'ambivalent'),
    (1,33,'gross'),
    (2,33,'puke');

-- update section 
update up set up.Note = db.Note
from @table1 up
inner join 
(
    select a.ItemNo,a.Note
    from @table1 a
    inner join 
    (
        select itemNo,Max(VersionID) as vs
        from @table1
        where Note <> ''
        group by itemNo
    ) as b on a.ItemNo = b.ItemNo and a.VersionID = b.vs
) as db on db.ItemNo = up.ItemNo and up.Note = ''


-- result
select * from @table1

Answer 5

You can select the maximum value for each " Item No. ", then update the original table with the corresponding value where the " Notes " is NULL.

UPDATE tab 
SET [Notes] = t2.[Notes]
FROM       tab t1 
INNER JOIN (SELECT *, MAX(Version) OVER(PARTITION BY [Item No.]) AS Max_Version
            FROM tab)  t2
        ON t1.[Item No.] = t2.[Item No.]
       AND t2.[Version]  = t2.[Max_Version]
       AND t1.[Notes] IS NULL

Check the demo here .