Product with last 4 vendors on transaction date

问题

Hi I have this sql and have to translate into NHibernate QueryOver

SELECT S.Number, S.Description, S.BrandDescription, subquery.vendornumber, subquery.vendorname
FROM Stocks.Stock S left join 
                    (select vendorNumber, VendorName, POLID, LastTransactionDate from
                        (
                        SELECT top 4 v.Number vendorNumber, v.Name VendorName, PLL.Id POLID, max(por.TransactionDate) as LastTransactionDate,
                        ROW_NUMBER() OVER(PARTITION BY v.Number ORDER BY max(por.TransactionDate) DESC) AS rk
                        FROM Purchasing.PurchaseOrderLineItem PLL 
                        inner join Purchasing.PurchaseOrder po on PLL.PurchaseOrderId = po.Id
                        inner join Purchasing.PurchaseOrderVendor POV on po.Id = POV.PurchaseOrderId
                        inner join Purchasing.Vendor V on pov.VendorId =  v.Id
                        left outer join Purchasing.PurchaseOrderReceipt POR on PLL.Id = por.PurchaseOrderLineItemId
                        group by v.Number, v.Name,PLL.Id
                        order by LastTransactionDate desc
                        ) subquery
                        where subquery.rk = 1) B on PL.Id = b.POLID

Or just to explain it simply see its simplified version

Select * from master m
outer apply (select top 4 * From Details d where m.Id = d.Id order by someColumns desc)o

I think we cannot use subquery as derived table in nhibernate. If you have suggestions, please share.

Thanks

回答1:

I was keep working on this and found that it could be very difficult if want to do totally with QueryOver. I want to show how I did this.

First I took all the vendors with StockID to join with StockQuery later.

            var stockVendors =
            Session.QueryOver<Vendor>(() => V)
                .Left.JoinQueryOver(p => V.Stock, () => sstk)
                .Where(sstk.Number !=null)
                .OrderBy(Projections.Max(() => V.TransactionDate)).Desc()
                .ThenBy(() => sstk.Number).Asc()
                .ThenBy(() => sv.Number).Asc()
                .SelectList(
                    lst =>
                    lst.SelectGroup(() => V.Name).WithAlias(() => svhModal.VendorName)
                        .SelectGroup(() => V.Number).WithAlias(() => svhModal.VendorNumber)
                        .SelectGroup(() => sstk.Number).WithAlias(() => svhModal.StockNumber)
                        .Select(Projections.Max(() => V.TransactionDate)).WithAlias(() => svhModal.LastTransactionDate)

) .TransformUsing(Transformers.AliasToBean()).List();

Then select Stock only

var stockDetail = Session.QueryOver<Stock>(() => stk)
            .Where(soneCriteria)
            .SelectList(list => list
                .Select(() => stk.Id).WithAlias(() => sdrModal.Id)
                .Select(() => stk.Number).WithAlias(() => sdrModal.Number)
.TransformUsing(Transformers.AliasToBean<StockDetailReportModal>())
                    .List<StockDetailReportModal>();

 IList<StockVendor> vlst2 = null;
            IList<StockDetail> newStock = new List<StockDetail>();

Here starts two loops to fill List object with each stock and its 5 top vendors from vendors list. Loop from Stockdetail result from query and inside loop from vendor result filtered to outer loop stockid, get first 5 vendors only in loop, when done just return the result to report. Its working fine.

foreach (StockDetail ostk in stockDetail)
        {
            stkid = ostk.Number;
            vlst2 = (from v in stockVendors where v.StockNumber == stkid orderby v.LastTransactionDate descending select v).ToList<StockVendor>();

            vndrcnt = 0;
            stok = new StockDetail
            {
                Id = ostk.Id,
                Number = ostk.Number,
//// other fields too here
            };

            if (vlst2.Count() == 0)
            {
                newStock.Add(stok);
            }

            foreach (StockVendor vn in vlst2)
            {
                if (vndrcnt == 0)
                {
                    stok.VendorName = vn.VendorName;
                    stok.VendorNumber = vn.VendorNumber;
          // other fields here...
                    newStock.Add(stok);
                }
                else
                {
                    newStock.Add(new StockDetail
                    {
                        Id = ostk.Id,
                        Number = ostk.Number,
                        VendorName = vn.VendorName,
                        VendorNumber = vn.VendorNumber,
// adding vendor information in stock record.
                        });
                    }
                    vndrcnt++;
                    if (vndrcnt >= 4)
                        break;
                }

This solved my problem and achieved this after investigating many days. You may find better approach, so please share.

来源：https://stackoverflow.com/questions/29113310/product-with-last-4-vendors-on-transaction-date