1. Creating Functions If you came to this presentation via a web browser, right-click and choose “Full Screen” before proceeding. Click mouse or press space bar to continue. This presentation was prepared by Professor Steve Ross, with the advice of other MIS Faculty, for use in MIS Classes at Western Washington University. Please contact Dr. Ross for permission to use in other settings..Dr. Ross

2. The Challenge Create functions that display a person’s name in a single field: –Last, First Middle –First Middle Last Functions should accommodate possibility of missing or null First and Middle Names

3. Design Before You Build What fields – from what tables – are required? –tblWorker LastName – Data Type: Text (30) FirstName – Data Type: Text (30) MidName – Data Type: Text (30) What additional characters (spaces, punctuation) are required? –Space after each non-blank first or mid name –Comma after last name when followed by non-blank first name

4. Creating the Function, Step 1 Functions are contained under Programmability in the database –Expand Programmability, then Functions –We will create a Scalar-valued Function –Right-click Scalar-valued Function, then choose New Scalar-valued Function… (see next slide)

5. Creating the Function, Step 2a Start by reading the note at the top of the screen that opens -- ================================================ -- Template generated from Template Explorer using: -- Create Scalar Function (New Menu).SQL -- -- Use the Specify Values for Template Parameters -- command (Ctrl-Shift-M) to fill in the parameter -- values below. -- -- This block of comments will not be included in -- the definition of the function. -- ================================================

6. Creating the Function, Step 2b Press Ctrl-Shift-M* and enter parameters: –Begin the function name with the “fn” prefix –Parameters and variables start with @ sign –We will add more parameters after pressing OK * Or select Query | Specify Values for Template Parameters

7. Creating the Function, Step 2c Add the other parameters, normal practice is to put each on a separate line, separated by commas. “ -- ” denotes a comment. -- ============================================= -- Author:Steve Ross -- Create date: 14-Jan-10 -- Description:Formats names: Last, First Middle -- ============================================= CREATE FUNCTION fnNameLast ( -- Add the parameters for the function here @first varchar(30), @middle varchar(30), @last varchar(30) )

8. Creating the Function, Step 2d Assign the value to be returned to the result variable: RETURNS varchar(60) AS BEGIN -- Declare the return variable here DECLARE @Result varchar(60) -- Add the T-SQL statements to compute the return value here SELECT @Result = @last SELECT @Result = @Result + ', ' + @first SELECT @Result = @Result + ' ' + @middle -- Return the result of the function RETURN @Result END GO

9. Creating the Function, Step 2e Execute the query, which should create the function. Right-click the database name, choose Refresh Your function should appear in the list:

10. Testing the Function I Click the New Query button Ensure that your database is selected Type a simple SELECT statement Execute the statement

11. Testing the Function II Modify the SELECT statement to refer to fields from a table Execute the statement

12. Appendix: Bullet-proofed Version This version handles problems that can arise when the data (names) contain Null or empty strings BEGIN -- This variable will hold the fullname DECLARE @FullNameBP varchar(75) -- Concatenate the name elements: first middle last -- Set @FullName to '', otherwise it will contain NULL SELECT @FullName = '' – Two single quotation marks IF (@FirstName IS NOT NULL) SELECT @FullName = @FullName + @FirstName -- Add [space] and middle name -- Trim leading [space] in case @FullName is still empty IF (@MidName IS NOT NULL) AND (@MidName <> '') SELECT @FullName = LTRIM(@FullName + ' ' + @MidName) -- Add [space] and last name -- Trim leading [space] in case @FullName is still empty IF (@LastName IS NOT NULL) AND (@LastName <> '') SELECT @FullName = LTRIM(@FullName + ' ' + @LastName) RETURN @FullName END