Home > Differences > Stored Procedures vs Functions (Difference between SP & UDF)

Stored Procedures vs Functions (Difference between SP & UDF)


Stored Procedures can contain a single SQL statement or a group of SQL statements with data flow control logic containing IF-ELSE, WHILE loop constructs, TRY-CATCH, transactions, etc.
SPs are used to return one or many result-sets to its calling application.

On the other hand Functions or UDFs can contain single or multiple SQL statements depending on its type. A Scalar UDF & Inline UDF can only have a single SELECT statement. And a Multi-Statement UDF can contain a body with multiple SQL statements including SELECTS, IF-ELSE, WHILE loops and DMLs but limited to manipulating table variables only.
UDFs return a single Scalar value or a Table variable to the calling SELECT statement.

Following are some common differences between an SP & a UDF:

Stored Procedures:
- Can be used to read and modify data.
- To run an SP Execute or Exec is used, cannot be used with SELECT statement.
- Cannot JOIN a SP in a SELECT statement.
- Can use Table Variables as well as Temporary Tables inside an SP.
- Can create and use Dynamic SQL.
- Can use transactions inside (BEGIN TRANSACTION, COMMIT, ROLLBACK) an SP.
- Can use used with XML FOR clause.
- Can use a UDF inside a SP in SELECT statement.
- Cannot be used to create constraints while creating a table.
- Can execute all kinds of functions, be it deterministic or non-deterministic.

Functions:
- Can only read data, cannot modify the database.
- Can only be used with SELECT statement, JOINS & APPLY (CROSS & OUTER).
- Can JOIN a UDF in a SELECT statement.
- Cannot use a Temporary Table, only Table Variables can be used.
- Cannot use a Dynamic SQL inside a UDF.
- Cannot use transactions inside a UDF.
- Cannot be used with XML FOR clause.
- Cannot execute an SP inside a UDF.
- Can be used to create Constraints while creating a table.
- Cannot execute some non-deterministic built-in functions, like GETDATE().

 

More on UDFs: http://sqlwithmanoj.wordpress.com/2010/12/11/udf-user-defined-functions/

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  1. Umayrr
    May 7, 2012 at 7:40 am | #1

    Thanks mate, I’m a web designer trying to develop things now, I was in need of some basics for SQL. This article somehow clarify my doubts concerning UDFs and SPs. Thumbs up.

  2. July 4, 2012 at 8:32 pm | #2

    thanks a lot…

  3. Naveen Dhayal
    August 16, 2012 at 5:05 pm | #3

    Very nice ….Thanks..Big Brother

  4. Ravindra
    August 18, 2012 at 9:19 pm | #4

    thanks

  5. May 15, 2013 at 4:22 pm | #5

    20 main differences between Stored procedures and Functions in Sql Server
    http://www.webcodeexpert.com/2013/04/difference-between-stored-procedures.html

  1. September 21, 2011 at 6:34 am | #1
  2. November 19, 2012 at 12:36 am | #2

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