Finding customers with identical orders

Question

I need to find customers who have made identical orders. (Using T-SQL)

Order

OrderID Customerer  
1   2   
2   5   
3   6            


        

Answer 1

Here's one way.

SELECT  O1.OrderID ,
        O1.Customer ,
        O2.OrderID ,
        O2.Customer
FROM    [Order] O1
        JOIN [Order] O2 ON O1.OrderID < O2.OrderID
                           AND O1.Customer <> O2.Customer
WHERE   NOT EXISTS ( SELECT Quantity ,
                            Reference
                     FROM   OrderLine
                     WHERE  O1.OrderID = OrderLine.OrderID
                     EXCEPT
                     SELECT Quantity ,
                            Reference
                     FROM   OrderLine
                     WHERE  O2.OrderID = OrderLine.OrderID )
        AND NOT EXISTS ( SELECT Quantity ,
                                Reference
                         FROM   OrderLine
                         WHERE  O2.OrderID = OrderLine.OrderID
                         EXCEPT
                         SELECT Quantity ,
                                Reference
                         FROM   OrderLine
                         WHERE  O1.OrderID = OrderLine.OrderID )

You can also use XML PATH to simulate GROUP_CONCAT then JOIN the two result sets

DECLARE @T TABLE
    (
      OrderId INT PRIMARY KEY,
      Customer INT ,
      complete_order VARCHAR(MAX)
    )  

    INSERT  INTO @T
            SELECT  *
            FROM    [Order] O
                    CROSS APPLY ( SELECT    CAST(Quantity AS VARCHAR(30))
                                            + '~' + Reference + '~~'
                                  FROM      OrderLine OL
                                  WHERE     OL.OrderID = O.OrderID
                                  ORDER BY  Reference ,
                                            Quantity
                                FOR
                                  XML PATH('')
                                ) T ( complete_order )

SELECT  T1.OrderId, 
        T1.Customer
FROM    @T T1
WHERE   EXISTS ( SELECT *
                 FROM   @T T2
                 WHERE  T1.Customer <> T2.Customer
                        AND T1.OrderId <> T2.OrderId
                        AND T1.complete_order = T2.complete_order )