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SQL Server FAQ - "ALTER FUNCTION" - Modifying Existing Functions

By: FYIcenter.com

(Continued from previous topic...)

How To Modify an Existing User Defined Function?

If you find a mistake in an existing function previously created, you can drop (delete) it and create it again correctly. But dropping a function may affect other database objects who are depending on this function.

So the best way to correct a mistake in an existing function is to use the "ALTER FUNCTION" statement as shown in the following tutorial example:

USE FyiCenterData;
GO

-- Modifying an existing function
ALTER FUNCTION Sundays()
   RETURNS INT
   AS BEGIN
      DECLARE @date DATETIME;
      DECLARE @count INT;
      SET @date = '2006-12-31'; 
      SET @count = 0;
      WHILE DATEPART(YEAR, @date) < 2008 BEGIN
         SET @date = DATEADD(DAY, 1, @date);
         IF DATENAME(WEEKDAY, @date) = 'Sunday' 
            SET @count = @count + 1;
         END;
      RETURN @count;
      END;
GO
Command(s) completed successfully.

Do you know what correction has been made on this function?

(Continued on next topic...)

  1. What Are User Defined Functions?
  2. What Are the Differences between User Defined Functions and Stored Procedures?
  3. How To Create a Simple User Defined Function?
  4. How To Use User Defined Functions in Expressions?
  5. How To List All User Defined Functions in the Current Database?
  6. How To Drop an Existing User Defined Function?
  7. How To Generate CREATE FUNCTION Script on an Existing Function?
  8. How To Get the Definition of a User Defined Function Back?
  9. How To Modify an Existing User Defined Function?
  10. How To Create User Defined Functions with Parameters?
  11. How To Provide Values to User Defined Function Parameters?
  12. Can You Pass Expressions to Function Parameters?
  13. How To Provide Default Values to Function Parameters?
  14. How Many Categories of Functions based Their Return Modes?
  15. How Many Ways to Create Table-Valued Functions?
  16. How To Create an Inline Table-Valued Function?
  17. How To Create an Multi-Statement Table-Valued Function?

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