SQL Pivot table error-using variable gives syntax error

Question

Hi my coworker came to me with this error and now I am hooked and trying to figure it out, hope some of the experts can help us! Thanks so much! When I execute Step6 we get this error:

Msg 102, Level 15, State 1, Line 4
Incorrect syntax near '@cols'.

---

--Sample of pivot query

--Creating Test Table Step1
CREATE TABLE Product(Cust VARCHAR(25), Product VARCHAR(20), QTY INT)
GO
-- Inserting Data into Table Step2
INSERT INTO Product(Cust, Product, QTY)
VALUES('KATE','VEG',2)
INSERT INTO Product(Cust, Product, QTY)
VALUES('KATE','SODA',6)
INSERT INTO Product(Cust, Product, QTY)
VALUES('KATE','MILK',1)
INSERT INTO Product(Cust, Product, QTY)
VALUES('KATE','BEER',12)
INSERT INTO Product(Cust, Product, QTY)
VALUES('FRED','MILK',3)
INSERT INTO Product(Cust, Product, QTY)
VALUES('FRED','BEER',24)
INSERT INTO Product(Cust, Product, QTY)
VALUES('KATE','VEG',3)
GO
-- Selecting and checking entires in table Step3
SELECT *
FROM Product
GO
-- Pivot Table ordered by PRODUCT Step4

select *
FROM (
SELECT *
FROM Product) up
PIVOT (SUM(QTY) FOR CUST IN ([FRED], [KATE])) AS pvt
ORDER BY PRODUCT
GO

--dynamic pivot???? Step5

DECLARE @cols NVARCHAR(2000)
select @cols =   STUFF(( SELECT DISTINCT TOP 100 PERCENT
                                '],[' + b.Cust
                        FROM    (select top 100 Cust
        from tblProduct)b
                        ORDER BY '],[' + b.Cust
                        FOR XML PATH('')
                      ), 1, 2, '') + ']'

--Show Step6

SELECT *
FROM (SELECT *
FROM tblProduct) p
PIVOT (SUM(QTY) FOR CUST IN (@cols)) as pvt
Order by Product

Answer 1

You would need dynamic SQL for this unfortunately.

declare @dyn nvarchar(max)
set @dyn = 'SELECT *
FROM (SELECT *
FROM Product) p
PIVOT (SUM(QTY) FOR CUST IN ('  +  @cols +')) as pvt
Order by Product
'
exec sp_executesql @dyn

Answer 2

@Martin Smith will be right...when you get to your next error. :-)

As for the error near @cols, I think you can just wrap the entire thing in parenthesis. E.g.:

select @cols = (
                   STUFF(( SELECT DISTINCT TOP 100 PERCENT
                                '],[' + b.Cust
                           FROM    (select top 100 Cust
                                    from tblProduct)b
                           ORDER BY '],[' + b.Cust
                           FOR XML PATH('')
                        ), 1, 2, '') + ']'
               )