User defined Function in SQL


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User defined Function in SQL

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User defined Function in SQL

  1. 1. Disclaimer: This presentation is prepared by trainees of baabtra as a part of mentoring program. This is not official document of baabtra –Mentoring Partner Baabtra-Mentoring Partner is the mentoring division of baabte System Technologies Pvt . Ltd
  2. 2. Week Target Achieved 1 ------- 15wpm 2 3 Typing Speed
  3. 3. Jobs Applied # Company Designation Applied Date Current Status 1 2 3
  4. 4. User Defined Functions In SQL Sandeep.v 9447532678
  5. 5. What is UDF? • User defined functions are similar to ordinary functions found in programming languages. • The main purpose of UDF is code reusability.
  6. 6. Benefits of using UDF • Modular programming. • Faster execution. • Code reusability.
  7. 7. • User defined functions can be passed input parameters • User defined functions are compiled and executed at runtime so pretty slower than stored procedures • UDF can’t perform DML (data manipulation language) operations like Insertion, Update and Deletion on the base table • UDF can’t return non deterministic values like GETDATE () etc • Stored procedure can’t be called from inside a UDF whereas a stored procedure can call a user defined function or another stored procedure inside it
  8. 8. Types of UDF… • Scalar functions • Returns a single value • Inline functions • Returns a table • Table values functions • Multiple operations, complex logic just like Stored procedures
  9. 9. FORMAT OF A UDF CREATE FUNCTION dbo.function_name ( @parameter1 datatype = default value, @parameter2 datatype ) RETURNS datatype AS BEGIN sql statements foms function body ... RETURN value END
  10. 10. SCALAR FUNCTION CREATE FUNCTION dbo.teach_name(@teachr_id int) RETURNS varchar(20) AS BEGIN Declare @returnvalue varchar(20) Select @returnvalue=teacher_name from tbl_teachers where teacher_id=@teachr_id RETURN @returnvalue END Execution: select dbo.teach_name(1002)as teacher_name
  11. 11. INLINE FUNCTION CREATE FUNCTION dbo.list_teach(@name varchar(10)) RETURNS TABLE AS RETURN SELECT * FROM tbl_teachers where teacher_name like '%'+@name+'%' Execution: select * from dbo.list_teach('i')
  12. 12. Table values functions CREATE FUNCTION udf_teach_day() RETURNS @Result TABLE ( vchr_teacher_name varchar(20) ,vchr_day varchar(10) ) AS BEGIN INSERT INTO @Result (vchr_teacher_name,vchr_day) select teacher_name,datepart(dw,teacher_doj)as vchr_day from tbl_teachers UPDATE @Result SET vchr_day = 'weekday' where vchr_day<>cast(2 as varchar(20)) UPDATE @Result SET vchr_day = 'monday' where vchr_day=cast(2 as varchar(20)) RETURN END
  13. 13. Execution:Select * from udf_teach_day()
  14. 14. Conclusion UDF are similar to functions in the programming languages, they provide a mechanism for extending the functionality of the database server by adding a function that can be evaluated in SQL statements.
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