DML in Functions

Question

DML in Functions

mithun.gite

SSCrazy

Points: 2333
More actions
April 22, 2009 at 1:42 am

#384413

Dear friends,
Need understanding, that y v cant perform DMLs in Functions?
We can use DMLs using table variable in fucntion then y can with actual tables..
Please guide me thru..
Mithun

Viewing 6 posts - 1 through 5 (of 5 total)

You must be logged in to reply to this topic. Login to reply

ChrisM@Work SSC Guru Points: 186127 More actions · Answer 1

mithun.gite (4/22/2009)
Dear friends,
Need understanding, that y v can perform DMLs in Functions?
We can use DMLs using table variable in fucntion then y can with actual tables..
Please guide me thru..
Mithun

From BOL:

The following statements are valid in a function:
Assignment statements.
Control-of-Flow statements except TRY...CATCH statements.
DECLARE statements defining local data variables and local cursors.
SELECT statements that contain select lists with expressions that assign values to local variables.
Cursor operations referencing local cursors that are declared, opened, closed, and deallocated in the function. Only FETCH statements that assign values to local variables using the INTO clause are allowed; FETCH statements that return data to the client are not allowed.
INSERT, UPDATE, and DELETE statements modifying local table variables.
EXECUTE statements calling extended stored procedures.
For more information, see Creating User-defined Functions (Database Engine).

Can you explain what you are trying to do?

^{“Write the query the simplest way. If through testing it becomes clear that the performance is inadequate, consider alternative query forms.” - Gail Shaw}

For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden

mithun.gite SSCrazy Points: 2333 More actions · Answer 2

Chris Morris (4/22/2009)
mithun.gite (4/22/2009)
Dear friends,
Need understanding, that y v can perform DMLs in Functions?
We can use DMLs using table variable in fucntion then y can with actual tables..
Please guide me thru..
Mithun
From BOL:
The following statements are valid in a function:
Assignment statements.
Control-of-Flow statements except TRY...CATCH statements.
DECLARE statements defining local data variables and local cursors.
SELECT statements that contain select lists with expressions that assign values to local variables.
Cursor operations referencing local cursors that are declared, opened, closed, and deallocated in the function. Only FETCH statements that assign values to local variables using the INTO clause are allowed; FETCH statements that return data to the client are not allowed.
INSERT, UPDATE, and DELETE statements modifying local table variables.
EXECUTE statements calling extended stored procedures.
For more information, see Creating User-defined Functions (Database Engine).
Can you explain what you are trying to do?

thanks chris for ur reply...........

after seeing ur reply i chekced my question which was bit wrong, which i corrected, actually i wan to know y we cant use DMLs in Functions?

Sorry for the trouble.......

And i m nothing trying but its been asked to me and i was clueless so i put it here..

Mithun

ChrisM@Work SSC Guru Points: 186127 More actions · Answer 3

From BOL, the first few sentences for CREATE FUNCTION:

Creates a user-defined function. This is a saved Transact-SQL or common language runtime (CLR) routine that returns a value. User-defined functions cannot be used to perform actions that modify the database state.

The purpose of a function is to return a value. For a simplistic model of why DML isn't supported in functions, consider this: you run a query which includes a function call against a table

SELECT *, myResult = dbo.fnDML(GETDATE(), dbo.fnGetWeather(GETDATE(), 'Reading, UK')) ...

- what's it going to do, add a column to a table if today is wednesday and it's sunny? Worse still, you could drop or add columns or even tables according to values in your source table. Row by row, the schema could change.

The structure of your db, which took months of careful design, is now all over the place.

^{“Write the query the simplest way. If through testing it becomes clear that the performance is inadequate, consider alternative query forms.” - Gail Shaw}

For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden

mithun.gite SSCrazy Points: 2333 More actions · Answer 4

Hey chris sir,,,

thanks for ur reply... now i know y we cant use dml in functions...

thanks , really thats usefulll

Mithun

ChrisM@Work SSC Guru Points: 186127 More actions · Answer 5

You're welcome - and I'm no 'sir', just a common working person, like yourself 😀

^{“Write the query the simplest way. If through testing it becomes clear that the performance is inadequate, consider alternative query forms.” - Gail Shaw}

For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden