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UDF Examples

In this section, I will present a few UDFs to help you get some idea of what you can accomplish with various sorts of UDFs.

The following scalar function returns a maximum amount of books sold for a specified title. This function should be executed in pubs database. If the title has no sales, the UDF will return zero.

/* scalar function to return max amount of books sold
** for the specified title_id
*/

CREATE FUNCTION dbo.udf_max_copies_sold_for_title (@title_id CHAR(6))
RETURNS INT
AS
BEGIN

DECLARE @qty INT
-- initialize the variable at 0:
SELECT @qty = 0

SELECT 
    @qty = MAX(qty) 
FROM sales 
WHERE
title_id = @title_id

/* If there are no books sold for title_id specified 
** then return 0:
*/
RETURN ISNULL(@qty, 0)

END

Now we can execute this function as follows:

SELECT dbo.udf_max_copies_sold_for_title ('bu2075')

Results:

----------- 
55

The following in-line function returns the product name, quantity ordered, and supplier for the top five best sellers in a particular year in the Northwind database:

/* in-line function to return quantity, product name and supplier
** for the top 5 best-selling products within the specified year
*/

CREATE FUNCTION dbo.udf_top_5_best_sellers (@year INT)
RETURNS TABLE
AS
RETURN

SELECT TOP 5 
     SUM(quantity) AS quantity_ordered, 
     a.ProductID, 
     ProductName, 
     CompanyName AS Supplier
FROM [order details] a INNER JOIN products b
   ON a.productid = b.productid
   INNER JOIN suppliers c ON c.supplierid = b.supplierid
   INNER JOIN orders d ON d.orderid = a.orderid
      AND DATEPART(YEAR, OrderDate) = @year
GROUP BY a.productid, productname, CompanyName
ORDER BY 1 DESC

We can execute this function as follows:

SELECT * FROM dbo.udf_top_5_best_sellers (1998)

Results:

quantity_ordered

ProductID

ProductName

Supplier

659

13

Konbu

Mayumi's

546

24

Guaraná Fantástica

Refrescos Americanas LTDA

542

60

Camembert Pierrot

Gai pturage

513

59

Raclette Courdavault

Gai pturage

414

7

Uncle Bob's Organic Dried Pears

Grandma Kelly's Homestead


Alternatively, we can SELECT only the desired columns from this function:

SELECT ProductID, 
        ProductName 
FROM dbo.udf_top_5_best_sellers (1998)

Results:

ProductID

ProductName

13

Konbu

24

Guaraná Fantástica

60

Camembert Pierrot

59

Raclette Courdavault

7

Uncle Bob's Organic Dried Pears


The following multi-statement function accepts a delimited list as a parameter parses the string and returns the table containing each of the values in the parameter.

/* multi-statement function to parse
** a delimited list and turn it into a rowset
** DEFAULT delimiter is comma
*/

CREATE FUNCTION dbo.parse_comma_delimited_integer(
    @list    VARCHAR(8000), 
    @delimiter VARCHAR(10) = ',')

-- table variable that will contain values
RETURNS @tablevalues TABLE (
    item INT)
AS
BEGIN 
  DECLARE @item VARCHAR(255)
 
  /* Loop over the commadelimited list */
  WHILE (DATALENGTH(@list) > 0)
    BEGIN 
      IF CHARINDEX(@delimiter,@list) > 0
        BEGIN
          SELECT @item =
             SUBSTRING(@list,1,(CHARINDEX(@delimiter, @list)-1))
          SELECT @list =
                SUBSTRING(@list,(CHARINDEX(@delimiter, @list) +
                DATALENGTH(@delimiter)),DATALENGTH(@list))
        END

     ELSE
        BEGIN
          SELECT @item = @list
          SELECT @list = NULL
        END
 
   -- Insert each item into temp table
    INSERT @tablevalues (
        item)
    SELECT item = CONVERT(INT, @item) 
   END

 RETURN
END

Now we can execute this function as follows:

SELECT * FROM dbo.parse_comma_delimited_integer 
('39, 549, 324, 3556, 24, 2132, 345', ',')

Results:

item

39

549

324

3556

24

2132

345


The following multi-statement UDF written for the Northwind database finds customers who have bought products in large quantities during a given year. The UDF accepts the year and amount of total sales and returns the customer name, the product that they have bought in large quantities, and all sales representatives who interfaced with these customers within the given year:

CREATE FUNCTION dbo.udf_top_customers_and_reps (
  @year INT, 
  @amount INT)

RETURNS 
  @temp TABLE(
    ProductName VARCHAR(200), 
    CategoryName VARCHAR(200),
    CustomerID CHAR(5),
    CompanyName VARCHAR(200),
    TotalSales INT, 
    EmployeeNames VARCHAR(2000))

AS 
BEGIN

/* populate the temp table with customers that have purchased any product 
* with total sales greater than the specified amount, within the given year
*/

INSERT @temp (
     ProductName ,
     CategoryName ,
     CompanyName ,
     CustomerID ,
     TotalSales 
)


SELECT 
    ProductName, 
    CategoryName, 
    CompanyName, 
    b.CustomerID, 
    SUM(a.UnitPrice * quantity) AS total_sales 
FROM [order details] a 
INNER JOIN orders b ON a.orderid = b.orderid
INNER JOIN products c ON c.productid = a.productid
INNER JOIN customers d ON d.customerid = b.customerid
INNER JOIN categories e ON e.CategoryID = c.CategoryID
WHERE DATEPART(YEAR, OrderDate) = @year
GROUP BY c.ProductName, e.CategoryName, b.CustomerID, 
d.CompanyName, DATEPART(YEAR, OrderDate) 
HAVING SUM(a.UnitPrice * quantity) > @amount
ORDER BY ProductName

/* now get all the employees that have been involved with the customers
* in the given year and return them in a comma-delimited list
*/


DECLARE @CustomerID CHAR(5), 
    @EmployeeName VARCHAR(200)

DECLARE @Employees TABLE (
	EmployeeName VARCHAR(80))

DECLARE CustomerCursor CURSOR FOR
SELECT CustomerID
FROM @temp a 

OPEN CustomerCursor
FETCH NEXT FROM CustomerCursor INTO @CustomerID

WHILE @@FETCH_STATUS = 0
BEGIN

INSERT @employees
SELECT DISTINCT FirstName + ' ' + LastName 
 FROM Employees a INNER JOIN Orders b ON a.EmployeeID = b.EmployeeID
 AND DATEPART(YEAR,OrderDate) = @year
 WHERE b.CustomerID = @CustomerID


/* create a comma-delimited list of employees */

SELECT @EmployeeName = ''
 SELECT @EmployeeName = @EmployeeName + ', ' + EmployeeName
 FROM @Employees	

SELECT @EmployeeName = SUBSTRING(@EmployeeName, 3, LEN(@EmployeeName)-2)



UPDATE @temp
SET EmployeeNames = @EmployeeName
WHERE CustomerID = @CustomerID

DELETE @Employees
FETCH NEXT FROM CustomerCursor INTO @CustomerID
END
CLOSE CustomerCursor
DEALLOCATE CustomerCursor


RETURN
END

The following execution of the function returns customers who have bought any product in amounts of over $10,000 during 1997:

SELECT * FROM dbo.udf_top_customers_and_reps (1997, 10000)

Results:

ProductName

CategoryName

CustomerID

Companyname

TotalSales

EmployeeNames

Côte de Blaye

Beverages

MEREP

Mère Paillarde

10329

Janet Leverling, Laura Callahan, Margaret Peacock, Michael Suyama, Nancy Davolio, Robert King

Côte de Blaye

Beverages

SIMOB

Simons bistro

10540

Andrew Fuller, Margaret Peacock, Robert King


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