Database

CREATE PROCEDURE cst 
@v char(10)
AS
SET DATEFORMAT dmy
SELECT * FROM col 
WHERE CASE WHEN ISDATE(col)=1 
	THEN CAST ( col AS DATETIME )ELSE CAST ( @v AS DATETIME )
	END < CAST ( @v AS DATETIME )
GO

SELECT a.*, b.*,
       SUM (orderPrice) AS totalPrice
  FROM tbl_Payment a 
        INNER JOIN tbl_Orders b ON a.paymentTable=b.orderTableID
                                AND a.paymentTable=b.orderUserID
WHERE orderPaid = false 
  AND orderTableID = '12' 
  AND orderUserID = 'Healey'

SELECT fieldList, 
       SUM (orderPrice) AS totalPrice  
  FROM tbl_Payment a
         INNER JOIN tbl_Orders b ON a.paymentTable=b.orderTableID
                                AND a.paymentTable=b.orderUserID
 WHERE orderPaid = false
   AND orderTableID = '12'   
   AND orderUserID = 'Healey'
GROUP BY fieldList

SELECT paymentTable
       , paymentName
       , paymentValue
       , SUM (orderPrice) AS totalPrice 
  FROM tbl_Payment a 
         INNER JOIN tbl_Orders b 
           ON a.paymentTable=b.orderTableID AND a.paymentName=b.orderUserID 
 WHERE orderPaid = false 
   AND orderTableID = '12' 
   AND orderUserID = 'Healey' 
GROUP BY paymentTable, paymentName, paymentValue