How to change my SQL Statement in PowerQuery

Hi Experts

I have a SQL statement that I can import to a Power Query

I received it from the supplier of our hotel system, but they are not very helpful apart from giving me the SQL code.

at the moment I can change the code in line 2 and I am able to see the specific date in Power Query.

I want to be able to import all days after a specific date, and afterwards I want my datamodel to be updated with new months

I am well aware, that the information might not be of the best quality, but hopefully you can guide me anyway

SELECT
  '01.06.2015' as 'DateStamp',
isnull(Accounts.ExportAccountNumber, Accounts.AccountNumber) as 'Account Number',
 Accounts.AccountText as 'Account Text',
 SUM(Transactions.PriceOverwrite * (CASE Transactions.Debit WHEN 1 THEN 1 ELSE -1 END)) as 'PriceOverWrite Without Vat',
 SUM(Transactions.PriceOverwrite * (CASE Transactions.Debit WHEN 1 THEN 1 ELSE -1 END)* CASE WHEN Accounts.AccountType IN (4,5,6) THEN 0 ELSE (VatValue/100) END) as 'PriceOverWrite Vat',
 0 as 'Reserved (AccountType)',
 isnull(Accounts.ExportDepartmentNumber, 110) as 'Export Department Number',
 
                (case when isnull(Accounts.ExportAccountNumber, Accounts.AccountNumber) = 20210 then 5 else
                case when isnull(Accounts.ExportAccountNumber, Accounts.AccountNumber) = 20215 then 6 else
                case when isnull(Accounts.ExportAccountNumber, Accounts.AccountNumber) = 20222 then 7 else
                case when isnull(Accounts.ExportAccountNumber, Accounts.AccountNumber) = 20248 then 5 else
                case when isnull(Accounts.ExportAccountNumber, Accounts.AccountNumber) = 20258 then 4 else null
                end
                end
                end
                end
                end)
             as 'Account alias',
 Customer.HotelNumber as 'Hotel Number',
 CASE WHEN (Reservations.Project IS NULL) THEN IsNull(Accounts.ExportProjectCodeNumber, 0) ELSE IsNUll(Reservations.ReferenceNumber, 0) END as 'ExportProjectcodeNumber',
 Departments.Departmentnumber as 'Active Department Number',
 99999 as 'Reserved (99999)'
FROM Accounts (NOLOCK)
 FULL OUTER JOIN TurnOverGroups WITH (NOLOCK) ON Accounts.TurnOverGroupNumber = TurnOverGroups.NUMBER
 FULL OUTER JOIN AccountGroups WITH (NOLOCK) ON Accounts.AccountGroupNumber = AccountGroups.AccountGroupNumber
 FULL OUTER JOIN Transactions WITH (NOLOCK) ON Accounts.AccountNumber = Transactions.AccountNumber
 INNER JOIN Folios WITH (NOLOCK) ON Folios.FolioNumber = Transactions.FolioNumber
 LEFT JOIN Reservations WITH (NOLOCK) ON (Reservations.ReferenceNumber = Folios.ReferenceNumber) AND (Reservations.GuestNumber = Folios.GuestNumber)
 LEFT OUTER JOIN Departments WITH (NOLOCK) ON Departments.PK_Department = Transactions.FK_DepartmentNumber
 INNER JOIN Customer WITH (NOLOCK) ON Customer.CustomerNumber = Transactions.HotelCustomerNumber
 INNER JOIN Ware WITH (NOLOCK) ON Ware.WareNumber = Transactions.WareNumber
 INNER JOIN WareGroups WITH (NOLOCK) ON WareGroups.WareGroupNumber = Ware.WareGroupNumber
WHERE
 convert(varchar,Transactions.DateStamp,112) > '20141125' AND
 Customer.HotelNumber in (0)
GROUP BY
 
                CASE WHEN (Reservations.Project IS NULL) THEN IsNull(Accounts.ExportProjectCodeNumber, 0) ELSE IsNUll(Reservations.ReferenceNumber, 0) END
            ,
 
                (case when isnull(Accounts.ExportAccountNumber, Accounts.AccountNumber) = 20210 then 5 else
                case when isnull(Accounts.ExportAccountNumber, Accounts.AccountNumber) = 20215 then 6 else
                case when isnull(Accounts.ExportAccountNumber, Accounts.AccountNumber) = 20222 then 7 else
                case when isnull(Accounts.ExportAccountNumber, Accounts.AccountNumber) = 20248 then 5 else
                case when isnull(Accounts.ExportAccountNumber, Accounts.AccountNumber) = 20258 then 4 else null
                end
                end
                end
                end
                end)
            ,
 Accounts.AccountNumber,
 Accounts.AccountText,
 Accounts.ExportAccountNumber,
 Accounts.ExportDepartmentNumber,
 Customer.HotelNumber,
 Departments.Departmentnumber
HAVING
 SUM(Transactions.PriceOverwrite * (CASE Transactions.Debit WHEN 1 THEN 1 ELSE -1 END)) <> 0
ORDER BY
  isnull(Accounts.ExportAccountNumber, Accounts.AccountNumber) ,
  isnull(Customer.HotelNumber, -1)