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sql server programming
group:newbie: create transaction in udf
sql server programming:
"Jeff" <it_consultant1@hotmail.com.NO_SPAM> wrote in message news:OL3dFUNnDHA.1728@TK2MSFTNGP09.phx.gbl... > sqlserver2000/win2k3 > > Why are these statements: > BEGIN TRANSACTION > ROLLBACK TRANSACTION > UPDATE (to a table created outside of the function) > COMMIT TRANSACTION > > not allowed in a function? > Conceptually it is because UDF's are an extension to the query engine, not stored procedures with return values. Allowing DML inside a query is too ugly and difficult to even contemplate. David
You can't have DDL/DML statements like those in a function (alter, drop,
create, update, insert, delete). I think you meant to use a stored procedure, not a udf. [quoted text, click to view] "Jeff" <it_consultant1@hotmail.com.NO_SPAM> wrote in message news:OL3dFUNnDHA.1728@TK2MSFTNGP09.phx.gbl... > sqlserver2000/win2k3 > > Why are these statements: > BEGIN TRANSACTION > ROLLBACK TRANSACTION > UPDATE (to a table created outside of the function) > COMMIT TRANSACTION > > not allowed in a function? > > Jeff > > > >
Functions are used to *RETURN* data (either a scalar or a table), not to
*AFFECT* data. As stated in the topic CREATE FUNCTION in Books Online, "Creates a user-defined function, which is a saved Transact-SQL routine that returns a value. User-defined functions cannot be used to perform a set of actions that modify the global database state." Also, see the topic "User-Defined Functions," which states: "The statements in a BEGIN...END block cannot have any side effects. Function side effects are any permanent changes to the state of a resource that has a scope outside the function such as a modification to a database table. The only changes that can be made by the statements in the function are changes to objects local to the function, such as local cursors or variables. Modifications to database tables, operations on cursors that are not local to the function, sending e-mail, attempting a catalog modification, and generating a result set that is returned to the user are examples of actions that cannot be performed in a function." I guess I'm curious what difference it makes what are the fundamental reasons behind this. Perhaps there is some code deep inside SQL Server that is used to make pancakes, and a side effect of executing such a statement in a function produces ketchup, and the SQL Server team does not like ketchup on their pancakes. The point is, they are not allowed. [quoted text, click to view] "Jeff" <it_consultant1@hotmail.com.NO_SPAM> wrote in message news:ukP1JgNnDHA.3316@tk2msftngp13.phx.gbl... > I know those statements are not allowed in a function, but don't know why > they are not allowed > > I know stored procedures works fine with this. > > So, i'm wondering why those statements are not allowed in a function.
sqlserver2000/win2k3
Why are these statements: BEGIN TRANSACTION ROLLBACK TRANSACTION UPDATE (to a table created outside of the function) COMMIT TRANSACTION not allowed in a function? Jeff
I know those statements are not allowed in a function, but don't know why
they are not allowed I know stored procedures works fine with this. So, i'm wondering why those statements are not allowed in a function. Jeff [quoted text, click to view] "Aaron Bertrand - MVP" <aaron@TRASHaspfaq.com> wrote in message news:eIuvxaNnDHA.1764@tk2msftngp13.phx.gbl... > You can't have DDL/DML statements like those in a function (alter, drop, > create, update, insert, delete). > > I think you meant to use a stored procedure, not a udf. > > > > > "Jeff" <it_consultant1@hotmail.com.NO_SPAM> wrote in message > news:OL3dFUNnDHA.1728@TK2MSFTNGP09.phx.gbl... > > sqlserver2000/win2k3 > > > > Why are these statements: > > BEGIN TRANSACTION > > ROLLBACK TRANSACTION > > UPDATE (to a table created outside of the function) > > COMMIT TRANSACTION > > > > not allowed in a function? > > > > Jeff > > > > > > > > > >
Thank you for taking the time to answer me. I have learned by reading your
answer. I'll read those topics in BOL tomorrow (it's 12pm here in norway, and I really have to go to sleep (log off)). [quoted text, click to view] "Aaron Bertrand - MVP" <aaron@TRASHaspfaq.com> wrote in message news:%23b%23rzpNnDHA.2432@TK2MSFTNGP10.phx.gbl... > Functions are used to *RETURN* data (either a scalar or a table), not to > *AFFECT* data. As stated in the topic CREATE FUNCTION in Books Online, > "Creates a user-defined function, which is a saved Transact-SQL routine that > returns a value. User-defined functions cannot be used to perform a set of > actions that modify the global database state." Also, see the topic > "User-Defined Functions," which states: > > "The statements in a BEGIN...END block cannot have any side effects. > Function side effects are any permanent changes to the state of a resource > that has a scope outside the function such as a modification to a database > table. The only changes that can be made by the statements in the function > are changes to objects local to the function, such as local cursors or > variables. Modifications to database tables, operations on cursors that are > not local to the function, sending e-mail, attempting a catalog > modification, and generating a result set that is returned to the user are > examples of actions that cannot be performed in a function." > > I guess I'm curious what difference it makes what are the fundamental > reasons behind this. Perhaps there is some code deep inside SQL Server that > is used to make pancakes, and a side effect of executing such a statement in > a function produces ketchup, and the SQL Server team does not like ketchup > on their pancakes. The point is, they are not allowed. > > > > > "Jeff" <it_consultant1@hotmail.com.NO_SPAM> wrote in message > news:ukP1JgNnDHA.3316@tk2msftngp13.phx.gbl... > > I know those statements are not allowed in a function, but don't know why > > they are not allowed > > > > I know stored procedures works fine with this. > > > > So, i'm wondering why those statements are not allowed in a function. > >
Ok
"David Browne" <davidbaxterbrowne no potted meat@hotmail.com> wrote in message news:O5nlHlNnDHA.360@TK2MSFTNGP12.phx.gbl... [quoted text, click to view] > "Jeff" <it_consultant1@hotmail.com.NO_SPAM> wrote in message > news:OL3dFUNnDHA.1728@TK2MSFTNGP09.phx.gbl... > > sqlserver2000/win2k3 > > > > Why are these statements: > > BEGIN TRANSACTION > > ROLLBACK TRANSACTION > > UPDATE (to a table created outside of the function) > > COMMIT TRANSACTION > > > > not allowed in a function? > > > > Conceptually it is because UDF's are an extension to the query engine, not > stored procedures with return values. > > Allowing DML inside a query is too ugly and difficult to even contemplate. > > David > >
[quoted text, click to view]
> I guess I'm curious what difference it makes what are the fundamental > reasons behind this. I agree that it might be some technical reason for this. However, IMO it is not that important whether such exist or not. Below is enough for me: SELECT MyFunc(col1) FROM tbl Imagine some modification being performed in the function above. I can't even start thinking about how that would work or how that would be perceived by the user. "Did you modify any data?" "No, honestly, I only did a SELECT..." "Smack!!!" ;-) -- Tibor Karaszi, SQL Server MVP Archive at: http://groups.google.com/groups?oi=djq&as_ugroup=microsoft.public.sqlserver [quoted text, click to view] "Aaron Bertrand - MVP" <aaron@TRASHaspfaq.com> wrote in message news:%23b%23rzpNnDHA.2432@TK2MSFTNGP10.phx.gbl... > Functions are used to *RETURN* data (either a scalar or a table), not to > *AFFECT* data. As stated in the topic CREATE FUNCTION in Books Online, > "Creates a user-defined function, which is a saved Transact-SQL routine that > returns a value. User-defined functions cannot be used to perform a set of > actions that modify the global database state." Also, see the topic > "User-Defined Functions," which states: > > "The statements in a BEGIN...END block cannot have any side effects. > Function side effects are any permanent changes to the state of a resource > that has a scope outside the function such as a modification to a database > table. The only changes that can be made by the statements in the function > are changes to objects local to the function, such as local cursors or > variables. Modifications to database tables, operations on cursors that are > not local to the function, sending e-mail, attempting a catalog > modification, and generating a result set that is returned to the user are > examples of actions that cannot be performed in a function." > > I guess I'm curious what difference it makes what are the fundamental > reasons behind this. Perhaps there is some code deep inside SQL Server that > is used to make pancakes, and a side effect of executing such a statement in > a function produces ketchup, and the SQL Server team does not like ketchup > on their pancakes. The point is, they are not allowed. > > > > > "Jeff" <it_consultant1@hotmail.com.NO_SPAM> wrote in message > news:ukP1JgNnDHA.3316@tk2msftngp13.phx.gbl... > > I know those statements are not allowed in a function, but don't know why > > they are not allowed > > > > I know stored procedures works fine with this. > > > > So, i'm wondering why those statements are not allowed in a function. > >
[quoted text, click to view]
"Aaron Bertrand - MVP" <aaron@TRASHaspfaq.com> wrote in message news:%23b%23rzpNnDHA.2432@TK2MSFTNGP10.phx.gbl... > I guess I'm curious what difference it makes what are the fundamental > reasons behind this. Perhaps there is some code deep inside SQL Server that > is used to make pancakes, and a side effect of executing such a statement in > a function produces ketchup, and the SQL Server team does not like ketchup > on their pancakes. The point is, they are not allowed. What? Are you okay? The difference it makes is that we are programmers, techies, people who as children were not happy until we had adjusted the TV until the knobs fell off and the antennas broke. This so we could rip the covers off and ask, how can I make it better, what makes it tick? If we just blindly let things like this go, they could do whatever they wanted to us. The more you understand the architecture of computers, the better a programmer you are. Do you understand how indexes are structured? Or do you you just know that they help you access data faster. Anyhow, if no one cared HOW stuff worked, Kalen would be out of business with her Inside SQL Server 2000 books, and you wouldn't want that :) -- ---------------------------------------------------------------------------- ----------- Louis Davidson (drsql@hotmail.com) Compass Technology Management Pro SQL Server 2000 Database Design http://www.apress.com/book/bookDisplay.html?bID=266 Note: Please reply to the newsgroups only unless you are interested in consulting services. All other replies will be ignored :)
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