How can I get the next value of the identity specification using SQL Server?
Don't say Select (id+1) from Table1, because it gives wrong results when deleting rows.
First of all, whatever you are doing, you are likely doing something wrong, because concurrency.
But you can get the next value of the identity column using
select ident_current('TableName') + ident_incr('TableName')
You can't know, and you aren't supposed to try to guess. It's important to rethink your problem. For example, stop using identity and generate your own IDs, or switch to something like uniqueidentifier instead, which you can control and won't clash between threads.
The identity value of the next record isn't deterministic. Consider this code;
begin tran
insert into table values ('my new value')
rollback tran
Even though this code doesn't insert a record, it will update the next ID generated, and cause a gap. So if the table were at max ID=4, then you run this code, then you do a insert which you commit, the ID of that record will be 6, not 5.
Because SQL Server controls this value, your predictions will be right only until your system hits more load, or people do advanced things like use transactions.
Its a classic source of problems, so avoid doing it.
An alternative, if you want to control IDs, is to use something like a HILO generator -- This RavenDB document explains the principle of the idea.
I have a stored procedure that contains dynamic select. Something like this:
ALTER PROCEDURE [dbo].[usp_GetTestRecords]
--#p1 int = 0,
--#p2 int = 0
#groupId nvarchar(10) = 0
AS
BEGIN
SET NOCOUNT ON;
DECLARE #query NVARCHAR(max)
SET #query = 'SELECT * FROM CUSTOMERS WHERE Id = ' + #groupId
/* This actually contains a dynamic pivot select statement */
EXECUTE(#query);
END
In SSMS the stored procedure runs fine and shows result set.
In C# using Entity Framework it shows returning an int instead of IEnumerable?
private void LoadTestRecords()
{
TestRecordsDBEntities dataContext = new TestRecordsDBEntities();
string id = ddlGroupId.SelectedValue;
List<TestRecord> list = dataContext.usp_GetTestRecords(id); //This part doesn't work returns int
GridView1.DataSource = list;
}
Generated function for usp_GetTestRecords
public virtual int usp_GetTestRecords(string groupId)
{
var groupIdParameter = groupId != null ?
new ObjectParameter("groupId", groupId) :
new ObjectParameter("groupId", typeof(string));
return ((IObjectContextAdapter)this).ObjectContext.ExecuteFunction("usp_GetTestRecords", groupIdParameter);
}
I get this when I have a stored procedure that includes an "exec" call into a temporary table, such as:
insert into #codes (Code, ActionCodes, Description)
exec TreatmentCodes_sps 0
It appears that Entity Framework gets confused as to what should be returned by the procedure. The solution I've come across is to add this at the top of the sproc:
SET FMTONLY OFF
After this, all is well.
I got the same problem, and found solution here
Move to your .edmx
At Model Browser Window/Function Imports find your procedure then double click it
Change the return type to you want
Save .edmx and check the return type again.
It should be what you need now.
Entity Framework can't tell what your stored procedure is returning. I've had success creating a table variable that mirrors the data from your SELECT statement. Just insert into the table variable then do a select from that table variable. EF should pick it up.
See Ladislav Mrnka's answer in this Stack Overflow post
https://stackoverflow.com/a/7131344/4318324
I had the same basic problem.
Adding
SET FMTONLY OFF
To a procedure you are trying to import during the import will address this problem.
It's a good practice to remove the line afterwards unless the purpose of the database is solely to provide schema for EF (Entity Framework).
The main reason for caution is that EF uses this setting to prevent data mutations when trying to obtain metadata.
If you refresh your entity model from a database any procedures with this line in them can potentially update the data in that database just by trying to obtain the schema.
I wanted to add a further note on this so it's not needed to fully scan through the other link.
if you want to try to use FMTONLY here are a couple things to keep in mind.
when FMTONLY is on:
1) only the schema is returned (no) rows.
similar to adding a blanket false statement to your where clause (ie "where 1=0")
2) flow control statements are ignored
Example
set fmtonly on
if 1=1
begin
select 1 a
end
else
begin
select 1 a,2 b
end
while 1=1
select 1 c
The above returns NO rows whatsoever and the metadata for each of the three queries
For this reason some people suggest toggling it off in a way that takes advantage of it's non-observance of flow control
if 1=0
begin
set fmtonly off
end
In fact you could use this to introduce logic that tracks this
set fmtonly off
declare #g varchar(30)
set #g = 'fmtonly was set to off'
if 1=0
begin
set fmtonly off
set #g = 'fmtonly was set to on'
end
select #g
Think VERY CAREFULLY before trying to use this feature as it is both deprecated and potentially makes sql extremely hard to follow
the MAIN concepts that need to be understood are the following
1. EF turns FMTONLY on to prevent MUTATING data from executing stored procedures
when it executes them during a model update.
(from which it follows)
2. setting FMTONLY off in any procedure that EF will attempt to do a schema scan
(potentially ANY and EACHONE) introduces the potential to mutate database
data whenever *anyone* attempts to update their database model.
Entity Framework will automatically return a scalar value if your stored procedure doesn't have a primary key in your result set. Thus, you'd have to include a primary key column in your select statement, or create a temp table with a primary key in order for Entity Framework to return a result set for your stored procedure.
I had the same problem, I changed the name of return fields by 'AS' keyword and addressed my problem. One reason for this problem is naming column names with SQL Server reserved keywords.
The example is fallows:
ALTER PROCEDURE [dbo].[usp_GetProducts]
AS
BEGIN
SET NOCOUNT ON;
SELECT
, p.Id
, p.Title
, p.Description AS 'Description'
FROM dbo.Products AS p
END
Best solution I found is to cheat a little.
In the store procedure, comment everything, put a first line with a select [foo]='', [bar]='' etc...
Now update the model, go to the mapped function, select complex type and click on Get Column Information and then Create Complex Type.
Now comment the fake select and un-comment the real store procedure body.
When you generated your model class for your stored procedure, you chose scalar return result by mistake. you should remove your stored procedure from your entity model, then re-add the stored procedure. In the dialog for the stored procedure, you can choose the return type you are expecting. Do not just edit the generated code.. this may work now, but the generated code can be replaced if you make other changes to your model.
I have pondered this a bit and I think I have a better/simpler answer
If you have a complex stored that gives entity framework some difficultly (for current versions of Entity Framework that are using the FMTONLY tag to aquire schema)
consider doing the folowing at the beginning of your stored procedure.
--where [columnlist] matches the schema you want EF to pick up for your stored procedure
if 1=0
begin
select
[columnlist]
from [table list and joins]
where 1=0
end
if you are okay loading your result set into a table variable
you can do the following to help keep your schema in sync
declare #tablevar as table
(
blah int
,moreblah varchar(20)
)
if 1=0
begin
select * from #tablevar
end
...
-- load data into #tablevar
select * from #tablevar
If you need to do this, then you might be better off just making a partial of the dbcontext and creating the C# function yourself that will use SqlQuery to return the data you need. Advantages over some of the other options is:
Don't have to change anything when the model updates
Won't get overwritten if you do it directly in the generated class (someone above mention this as if it's an option :) )
Don't have to add anything to the proc itself that could have side effects now or later on
Example Code:
public partial class myEntities
{
public List<MyClass> usp_GetTestRecords(int _p1, int _p2, string _groupId)
{
// fill out params
SqlParameter p1 = new SqlParameter("#p1", _p1);
...
obj[] parameters = new object[] { p1, p2, groupId };
// call the proc
return this.Database.SqlQuery<MyClass>(#"EXECUTE usp_GetTestRecords #p1, #p2, #groupId", parameters).ToList();
}
}
Just change to
ALTER PROCEDURE [dbo].[usp_GetTestRecords]
--#p1 int = 0,
--#p2 int = 0
#groupId nvarchar(10) = 0
AS
BEGIN
SET NOCOUNT ON;
SELECT * FROM CUSTOMERS WHERE Id = #groupId
END
I know this is an old thread but in case someone has the same problems I'll tell my woes.
As a help to find the issue, run sql profiler when you add your stored proc. Then you can see what entity framework is passing as parameters to generate your resultset. I imagine nearly always it will pass null parameter values. If you are generating sql on the fly by concatenating string values and parameter values and some are null then the sql will break and you wont get a return set.
I haven't needed to generate temp tables or anything just an exec command.
Hope it helps
During import
SET FMTONLY ON
can be used for taking the sp schema.
If you change the sp and want to update the new one, you should delete the old defined function from edmx file (from xml), because although deleting sp from model browser, it is not deleted in edmx. For example;
<FunctionImport Name="GetInvoiceByNumber" ReturnType="Collection(Model.Invoice_Result)">
<Parameter Name="InvoiceNumber" Mode="In" Type="Int32" />
</FunctionImport>
I had the same problem, and when I delete the FuctionImport tag of corresponding sp totally, the model updated right. You can find the tag by searching the function name from visual studio.
You may have luck opening up the model browser, then going to Function Imports, double clicking the stored procedure in question and then manually clicking "Get Column Information" and then clicking "Create New Complex Type". This usually sorts out the problem.
Well I had this issue as well but after hours of online searching none of above methods helped.
Finally I got to know that It will happen if your store procedure is getting some parameters as null and which generate any error in query execution.
Entity Framework will generate method for store procedure by defining the complex entity model. Due to that null value your store procedure will return and int value.
Please check your store procedure either its providing empty result set with null values. It will fix your problem. Hopefully.
I think this is a problem of permissions on the database, I don't know what exactly could be, but, in my job we use Active Directory users to grant applications connect to databases, this accounts are specially created for the applications, each app has its own user account, well, as a developers I have permissions for read, write and other basic things, no alter, and no advanced features, and I have this same problem running Visual Studio with my normal account, then, what I did was to open Visual Studio selecting the option "as a different user" on the context menu, and I put the AD login granted for the application and voila!, now my Stored Procedures are loading with all the fields I was expected, before that, my Stored Procedures was returning as int. I hope this help someone, maybe the VIEW DEFINITION permissions on database account do the trick
If SQL Authentication is in place, verify that the user credential that is being used to connect Entity Framework to the database has the proper rights to read from CUSTOMERS table.
When Entity Framework uses SQL Authentication to map complex objects (i.e stored procedures that SELECTs more than one column), if any of the tables from within such stored procedure don't have set up the Read permission, the mapping will result in returning INT instead of the desired Result set.
I have created two threads in C# and I am calling two separate functions in parallel. Both functions read the last ID from XYZ table and insert new record with value ID+1. Here ID column is the primary key. When I execute the both functions I am getting primary key violation error. Both function having the below query:
insert into XYZ values((SELECT max(ID)+1 from XYZ),'Name')
Seems like both functions are reading the value at a time and trying to insert with the same value.
How can I solve this problem.. ?
Let the database handle selecting the ID for you. It's obvious from your code above that what you really want is an auto-incrementing integer ID column, which the database can definitely handle doing for you. So set up your table properly and instead of your current insert statement, do this:
insert into XYZ values('Name')
If your database table is already set up I believe you can issue a statement similar to:
alter table your_table modify column you_table_id int(size) auto_increment
Finally, if none of these solutions are adequate for whatever reason (including, as you indicated in the comments section, inability to edit the table schema) then you can do as one of the other users suggested in the comments and create a synchronized method to find the next ID. You would basically just create a static method that returns an int, issue your select id statement in that static method, and use the returned result to insert your next record into the table. Since this method would not guarantee a successful insert (due to external applications ability to also insert into the same table) you would also have to catch Exceptions and retry on failure).
Set ID column to be "Identity" column. Then, you can execute your queries as:
insert into XYZ values('Name')
I think that you can't use ALTER TABLE to change column to be Identity after column is created. Use Managament Studio to set this column to be Identity. If your table has many rows, this can be a long running process, because it will actually copy your data to a new table (will perform table re-creation).
Most likely that option is disabled in your Managament Studio. In order to enable it open Tools->Options->Designers and uncheck option "Prevent saving changes that require table re-creation"...depending on your table size, you will probably have to set timeout, too. Your table will be locked during that time.
A solution for such problems is to have generate the ID using some kind of a sequence.
For example, in SQL Server you can create a sequence using the command below:
CREATE SEQUENCE Test.CountBy1
START WITH 1
INCREMENT BY 1 ;
GO
Then in C#, you can retrieve the next value out of Test and assign it to the ID before inserting it.
It sounds like you want a higher transaction isolation level or more restrictive locking.
I don't use these features too often, so hopefully somebody will suggest an edit if I'm wrong, but you want one of these:
-- specify the strictest isolation level
SET TRANSACTION ISOLATION LEVEL SERIALIZABLE
insert into XYZ values((SELECT max(ID)+1 from XYZ),'Name')
or
-- make locks exclusive so other transactions cannot access the same rows
insert into XYZ values((SELECT max(ID)+1 from XYZ WITH (XLOCK)),'Name')
I have been using a stored procedure for more than 1.5 years. But I've never considered how data is retrieved from the UI or within another stored procedure.
When I write a simple stored procedure.
eg.
CREATE PROCEDURE sp_test
AS
BEGIN
SELECT * FROM tblTest --Considering table has 3 columns.
END
How does C# gets this result into DataTable.
Whenever I have to use the result of this procedure in another procedure, I think we have to create a table valued parameter using the table datatype and assign its result to a table variable. I've never tried it.
CREATE PROCEDURE sp_testcall
AS
BEGIN
#temp = exec sp_test -- I think this would be the way, never tried
END
If the above sample code is true, then what is the difference between using the above method and a query to insert records into a temporary table?
CREATE PROCEDURE sp_test
AS
BEGIN
SELECT * INTO #tmp FROM tblTest --Considering table has 3 columns.
END
It would seem that copying the result into a temporary table requires another effort by sql server.
But what would be going on behind the scenes? Would it directly assign references of the result into a table valued parameter or does it use the same process as a temporary table?
My question might not be clear. But I will try to improve.
For an beginer to intermediate level you should always consider #temp tables and #table variables two faces of the same coin. While there are some differences between them, for all practical purposes they cost the same and behave nearly identical. The sole major difference is that #table variables are not transacted and hence not affected by rollbacks.
If you drill down into details, #temp tables are slightly more expensive to process (since they are transacted) but on the other hand #table variables have only the lifetime of a variable scope.
As to other issues raised by your question:
table value parameters are always read only and you cannot modify them (insert/update/delete into them)
tacking the result set of a procedure into a table (real table, #temp table or #tabel variable, doesn't matter) can only be done by using INSERT INTO <table> EXEC sp_test
as a rule of thumb a procedure that produces a result that is needed in another procedure is likely to be better of as a User Defined Function
The topic of sharing data between procedures was analyzed at length by Erland Sommarskog, see How to Share Data Between Stored Procedures.
A select means "return data to client". C# is a client, therefore it gets the data.
Then again, it's not exactly C# that does it, it's ADO.NET. There's a data provider that knows how to use a network/memory/some other protocol to talk to the SQL server and read data streams it generates. This particular client (ADO.NET) uses the received data to construct certain classes, such as DataTable, other providers can do something completely different.
All that is irrelevant at SQL Server level, because as far as the server is concerned, the data has been sent out using the protocol with which the connection was established, that's it.
From inside, it doesn't make much sense to have a stored procedure return simply selected data to anything else.
When you need to do that, you have the means to explicitly tell SQL Server what you want, such as inserting the data into a temporary table available to both involved SPs, inserting data into a table-valued parameter passed to the procedure, or rewriting your stored procedure as a function that returns a table.
Then again, it's not exacly clear to me what you were asking about.
SET NOCOUNT ON stops the message that shows the count of the number of rows affected by a Transact-SQL statement or stored procedure from being returned as part of the result set.
a) How can you read these messages using C# and ADO.NET ( I assume C# code reading these messages is the same regardless of whether T-SQL statements were executed in a stored procedure, batch or… )?
b) Assuming stored procedure contains several statements, how can your C# code identify to what SQL statement does particular messages refer to?
Thank you
Informational messages (like the rows affected count info) are reported in ADO.Net through the SqlConnection.InfoMessage event. Add a delegate to the event and will be invoked whenever the server transmits an informational message (ie. any error message with severity bellow 10).
there is no way to associate informational messages like afffected count info with the source. You're going to have to do it based on knowledge of the logic and understand that the first message refers to the first update, the second message to the second update etc.
Relying on affected rows count in the client is generaly a bad practice. The many issues ORM layers like NHibernate and ADO.Net datasets have when SET NOCOUNT ON is turned on just shows how problematic this practice is.
Don't rely on it. Best practice is SET NOCOUNT ON (discussed with my question here)
When you load your datatable, use .Count.
Use an OUTPUT parameter to pass ##ROWCOUNT back (or as a dataset)
Take a look at this question and answers. You can't do (b) above without adding some code in your TSQL that captures the ##rowcount and outputs it in some manner (like a resultset that you could read from).
One option is in your stored procedure is to include variables that you will pass back statement counts. You can do by creating your procedure with the needed OUTPUT parameters.
FIRST SQL HERE
#FirstSQLCount = ##ROWCOUNT
SECOND SQL HERE
#SecondSQLCount = ##ROWCOUNT