SQL Server：仅当一列的计数大于另一列的计数时才返回数据

Question

What I want to do:

If the total number of occurrences of a serial number in table OITM ( OITM.AssetSerNo ) is greater than the total number of occurrences of the same serial number in RDN1 ( RDN1.SerialNum ), then I want to return a few fields from the OITM record with the matching serial number where the Asset Number OITM.ItemCode (PKey) is greatest.

The code I have is as follows

select 

oitm.itemcode as 'Asset No', 
oitm.itemname as 'Asset Description',
oitm.assetSerNo as 'Serial No'

from oitm
inner join rdn1 on oitm.assetserno = rdn1.serialnum

WHERE
OITM.itemtype = 'F'
and OITM.asststatus = 'A'

HAVING count(oitm.assetserno)>count(rdn1.serialnum)

Unfortunately, I'm getting an error because the majority of my items are neither in a group by or an aggregate function. I'm not even sure the HAVING clause is the best way to approach the problem (in fact, I'm fairly sure that it's not).

EDIT: Sample data (I guess?)

OITM

ItemCode        ItemName        AssetSerNo        ItemType       AsstStatus
123             Object 1        QW                F              I
234             Object 2        ER                F              A
345             Object 3        RT                F              I
456             Object 4        TY                F              A
567             Object 1        QW                F              I
678             Object 5        YU                F              I
789             Object 3        RT                F              A
890             Object 1        QW                F              A
901             Object 2        UI                F              A

This is an item master list data record. A = active, I = inactive.

RDN1

DocID           Object Name     Serial Num 
1               Object 1        QW
2               Object 3        RT
3               Object 1        QW
4               Object 5        YU
5               Object 4        TY
6               Object 3        RT

This is a list of return records, for when the rented items return to the warehouse.

Expected output:

ItemCode        ItemName        AssetSerNo 
789             Object 3        RT
456             Object 4        TY

I need a list of all items where a return has been created, but the item has not been made inactive yet. I can't just do an inner join on RDN1 because I may have items that are returned, the item record is changed to I, but then it's sent back out and a new item record is created.

Answer 1

20 different ways to do this and they are all right. Here is the way using most of your code and implementing an EXISTS() command.

select 
 oitm.itemcode as 'Asset No', 
 oitm.itemname as 'Asset Description',
 oitm.assetSerNo as 'Serial No'
from oitm x
WHERE
 EXISTS(
  select TOP 1 1 
  from oitm y
   inner join rdn1 z on y.assetserno = z.serialnum
  WHERE
   y.itemtype = 'F'
   and y.asststatus = 'A'
   and y.assetSerNo = x.assetSerNo 
  HAVING count(y.assetserno)>count(z.serialnum)
)

Answer 2

here's an option using some sub queries

SELECT 
    item.itemcode AS 'Asset No',
    item.itemname AS 'Asset Description',
    item.assetSerNo AS 'Serial No'
FROM
(
    SELECT
        oitm.itemcode,
        oitm.itemname,
        oitm.assetSerNo,
        COUNT() OVER (PARTITION BY assetSerNo) assetSerNoCount,
        ROW_NUMBER() OVER (PARTITION BY assetSerNo ORDER BY oitm.itemcode DESC) rn
    FROM
        oitm
    WHERE
        OITM.itemtype = 'F'
        AND OITM.asststatus = 'A'
) item
LEFT JOIN (
    SELECT 
        serialnum, COUNT(*) serialnumCount 
    FROM 
        rdn1 
    GROUP BY 
    serialnum
) serial ON serial.serialnum = item.assetSerNo
WHERE
    ISNULL(serial.serialnumCount,0) < item.assetSerNoCount
    AND item.rn = 1