we're sending data from a Oracle-Server to a SQL-Server.
What I would like to do on the SQL-Side: I'd like to select data, which was inserted on the Oracle-side, to make some Insert/Update checks.
So a example:
On Oracle side I insert a value on the Table LANG_PARAM:
insert into lang_param
values p_rec
;
On the SQL-Server side, I try to read out the data and fill it in a parameter:
SELECT #Id = LANG_PARAM_ID
FROM LANG_PARAM
WHERE LANG_PARAM_ID = #lang_Param_Id
But I always get null back. Since I didn't find anything about this case, it is just not possible or do I need to set something?
P.S. I cutted the Linked-Server name at the select ,but it'd be there.
Thanks in advance and a good start in the week.
Matthias
Related
I have a stored procedure that relies on a query to a linked server.
This stored procedure is roughly structured as follows:
-- Create local table var to stop query from needing round trips to linked server
DECLARE #duplicates TABLE (eid NVARCHAR(6))
INSERT INTO #duplicates(eid)
SELECT eid FROM [linked_server].[linked_database].[dbo].[linked_table]
WHERE es = 'String'
-- Update on my server using data from linked server
UPDATE [my_server].[my_database].[dbo].[my_table]
-- Many things, including
[status] = CASE
WHEN
eid IN (
SELECT eid FROM #duplicates
)
THEN 'String'
ELSE es
END
FROM [my_server].[another_database].[dbo].[view]
-- This view obscures sensitive information and shows only the data that I have permission to see
-- Many other things
The query itself is much more complex, but the key idea is building this temporary table from a linked server (because it takes the query 5 minutes to run if I don't, versus 3 seconds if I do).
I've recently had an issue where I ended up with updates to my table that failed to get checked against the linked server for duplicate information.
The logical chain of events is this:
Get all of the data from the original view
The original view contains maybe 3000 records, of which maybe 30 are
duplicates of the entity in question, but with 1 field having a
different value.
I then have to grab data from a different server to know which of
the duplicates is the correct one.
When the stored procedure runs, it updates each record.
ERROR STEP - when the stored procedure hits a duplicate record, it
updates my_table again - so es gets changed multiple times in a row.
The temp table was added after the fact when we realized incorrect es values were being introduced to my_table.
'my_database` does not contain the data needed to determine which is the correct tuple, hence the requirement for the linked server.
As far as I can tell, we had a temporary network interruption or a connection timeout that stopped my_server from getting the response back from linked_server, and it just passed an empty table to the rest of the procedure.
So, my question is - how can I guard against this happening?
I can't just check if the table is empty, because it could legitimately be empty. I need to definitively know if that initial SELECT from linked_server failed, if it timed out, or if it intentionally returned nothing.
without knowing the definition of the table you're querying you could get into an issue where your data is to long and you get a truncation error on your table.
Better make sure and substring it...
DECLARE #duplicates TABLE (eid NVARCHAR(6))
INSERT INTO #duplicates(eid)
SELECT SUBSTRING(eid,1,6) FROM [linked_server].[linked_database].[dbo].[linked_table]
WHERE es = 'String'
-- Update on my server using data from linked server
UPDATE [my_server].[my_database].[dbo].[my_table]
-- Many things, including
[status] = CASE
WHEN
eid IN (
SELECT eid FROM #duplicates
)
THEN 'String'
ELSE es
END
FROM [my_server].[another_database].[dbo].[view]
I had a similar problem where I needed to move data between servers, could not use a network connection so I ended up doing BCP out and BCP in. This is fast, clean and takes away the complexity of user authentication, drivers, trust domains. also it's repeatable and can be used for incremental loading.
I want to insert some data on the local server into a remote server, and used the following sql:
select * into linkservername.mydbname.dbo.test from localdbname.dbo.test
But it throws the following error
The object name 'linkservername.mydbname.dbo.test' contains more than the maximum number of prefixes. The maximum is 2.
How can I do that?
I don't think the new table created with the INTO clause supports 4 part names.
You would need to create the table first, then use INSERT..SELECT to populate it.
(See note in Arguments section on MSDN: reference)
The SELECT...INTO [new_table_name] statement supports a maximum of 2 prefixes: [database].[schema].[table]
NOTE: it is more performant to pull the data across the link using SELECT INTO vs. pushing it across using INSERT INTO:
SELECT INTO is minimally logged.
SELECT INTO does not implicitly start a distributed transaction, typically.
I say typically, in point #2, because in most scenarios a distributed transaction is not created implicitly when using SELECT INTO. If a profiler trace tells you SQL Server is still implicitly creating a distributed transaction, you can SELECT INTO a temp table first, to prevent the implicit distributed transaction, then move the data into your target table from the temp table.
Push vs. Pull Example
In this example we are copying data from [server_a] to [server_b] across a link. This example assumes query execution is possible from both servers:
Push
Instead of connecting to [server_a] and pushing the data to [server_b]:
INSERT INTO [server_b].[database].[schema].[table]
SELECT * FROM [database].[schema].[table]
Pull
Connect to [server_b] and pull the data from [server_a]:
SELECT * INTO [database].[schema].[table]
FROM [server_a].[database].[schema].[table]
I've been struggling with this for the last hour.
I now realise that using the syntax
SELECT orderid, orderdate, empid, custid
INTO [linkedserver].[database].[dbo].[table]
FROM Sales.Orders;
does not work with linked servers. You have to go onto your linked server and manually create the table first, then use the following syntax:
INSERT INTO [linkedserver].[database].[dbo].[table]
SELECT orderid, orderdate, empid, custid
FROM Sales.Orders
WHERE shipcountry = 'UK';
I've experienced the same issue and I've performed the following workaround:
If you are able to log on to remote server where you want to insert data with MSSQL or sqlcmd and rebuild your query vice-versa:
so from:
SELECT * INTO linkservername.mydbname.dbo.test
FROM localdbname.dbo.test
to the following:
SELECT * INTO localdbname.dbo.test
FROM linkservername.mydbname.dbo.test
In my situation it works well.
#2Toad: For sure INSERT INTO is better / more efficient. However for small queries and quick operation SELECT * INTO is more flexible because it creates the table on-the-fly and insert your data immediately, whereas INSERT INTO requires creating a table (auto-ident options and so on) before you carry out your insert operation.
I may be late to the party, but this was the first post I saw when I searched for the 4 part table name insert issue to a linked server. After reading this and a few more posts, I was able to accomplish this by using EXEC with the "AT" argument (for SQL2008+) so that the query is run from the linked server. For example, I had to insert 4M records to a pseudo-temp table on another server, and doing an INSERT-SELECT FROM statement took 10+ minutes. But changing it to the following SELECT-INTO statement, which allows the 4 part table name in the FROM clause, does it in mere seconds (less than 10 seconds in my case).
EXEC ('USE MyDatabase;
BEGIN TRY DROP TABLE TempID3 END TRY BEGIN CATCH END CATCH;
SELECT Field1, Field2, Field3
INTO TempID3
FROM SourceServer.SourceDatabase.dbo.SourceTable;') AT [DestinationServer]
GO
The query is run on DestinationServer, changes to right database, ensures the table does not already exist, and selects from the SourceServer. Minimally logged, and no fuss. This information may already out there somewhere, but I hope it helps anyone searching for similar issues.
In Sql Server I am using an XML type column to store a message. I do not want to store duplicate messages.
I only will have a few messages per user. I am currently querying the table for these messages, converting the XML to string in my C# code. I then compare the strings with what I am about to insert.
Unfortunately, Sql Server pretty-prints the data in the XML typed fields. What you store into the database is not necessarily exactly the same string as what you get back out later. It is functionally equivalent, but may have white space removed, etc.
Is there an efficient way to compare an XML string that I am considering inserting with those that are already in the database? As an aside, if I detect a duplicate I need to delete the older message then insert the replacement.
0 - Add a hash column to your table
1 - when you receive a new message, convert the whole XML to uppercase, remove all blanks and returns/linefeed, then compute the hash value of the normalized string.
2 - check if you already have a row with the resulting hash code in it.
If yes, this is duplicated, treat it
accordingly
If not, store the original XML along with the hash in a new row
I'm not 100% sure on your exact implementation but here is something I played around with. The idea being a stored procedure would do the inserting. Inserting into the messages table does a basic check on existing messages (SQL 2008 syntax):
declare #messages table (msg xml)
insert into #messages values
('<message>You like oranges</message>')
,('<message>You like apples</message>')
declare #newMessage xml = '<message>You like apples</message>'
insert into #messages (msg)
select #newMessage
where #newMessage.value('(message)[1]', 'nvarchar(50)') not in (
select msg.value('(message)[1]', 'nvarchar(50)')
from #messages
)
One solution is to stop using the XML typed field. Store the XML string into a varchar typed field.
I don't really like this solution, but I don't really like p.marino's solution either. It doesn't seem right to store a hash of something that is already in the row in the table.
What if you use OPENXML on each row in the table and query the actual XML information for key nodes and/or key attributes? But then you need to do it row by row, I don't think OPENXML works with a whole set of table rows.
Some how some records in my table are getting updated with value of xyz in a certain column. Out of hundred of stored procedures, functions, triggers, how can I determine which code is doing this action. Is there a way to search through the database some how through each and every script of the code?
Please help.
One approach is to check syscomments
Contains entries for each view, rule,
default, trigger, CHECK constraint,
DEFAULT constraint, and stored
procedure within the database. The
text column contains the original SQL
definition statements..
e.g. select text from syscomments
If you are having trouble finding that literal string, the values could be coming from a table, or they could be being concatenated within a routine.
Try this
Select text from syscomments
where CharIndex('x', text) > 0
and CharIndex('y', text) > 0
and CharIndex('z', text) > 0
That might help you either find the right routine, or further indicate that the values are coming from a table.
This is going to be nearly impossible to do in SQL Server 2000 because the update might very well be from a variable that has that value or a join to another table that has that value and not hard-coded into the stored proc, trigger etc. The update could also be coming from a DTS package, a job, a piece of dynamic code run by the app or even from query analyzer, so the code itself may not be recorded inthe datbase anywhere.
Perhaps a better approach might be to create an audit table for the table in question and have it record the user and the code from the spid that generated the change as well as the old and new values. You'll have to wait until it happens again, but then you would know exactly what changed the value and what value to put it back to if need be.
Alternatively you could run profiler on the system until it happens but profiler tends to hurt performance and is not usually a good idea to run on a production system. If it is happening very often, it might be an acceptable alternative.
Here's a hint as to how you might get some of the info you want for the eventual trigger code you write:
create table #temp (eventtype nvarchar (1000), parameters int, eventinfo nvarchar (4000), myspid int)
declare #myspid int
select #myspid =##spid
insert #temp (eventtype,parameters, eventinfo)
exec ('dbcc inputbuffer (##spid)')
update #temp
set myspid = #myspid
select hostname, program_name, eventinfo
from #temp t
join sysprocesses s on t.myspid = s.spid
WHERE spid = #myspid
You might use sql-profiler to trac the update of a given table / column.
I have a web application (ASP.net 2.0) that has a database (SQL Server) at the background. I'm considering ways how to handle database concurrency if two users insert the same data to the same table at the same time. Are there any way to handle this case? Thanks in advance.
Jimmy
To prevent the same data being INSERTed at the same time, use a unique index on the columns that you want to be unique. The first INSERT will succeed, handle the error for the losing INSERT appropriately.
To prevent 2+ users from modifying the same (existing) record at the same time, use optimistic concurrency http://en.wikipedia.org/wiki/Optimistic_concurrency_control. With SQL Server it's easy to implement optimistic concurrency using a TIMESTAMP column. Read the timestamp with your data. When updating the row, check that the timestamp value is the same. If the timestamps don't match, then the user had (was viewing) an outdated row. Handle that case appropriately.
An example using SqlClient:
command.CommandText = #"
UPDATE tbl
SET LastName = #LastName, FirstName = #FirstName
WHERE ID = #ID AND Timestamp = #Timestamp
";
int rowCount = command.ExecuteNonQuery();
if (rowCount != 1)
throw new DBConcurrencyException();
All you need is:
BEGIN TRANSACTION;
INSERT XXXXXX INTO TABLE1 ......
INSERT YYYYY INTO TABLE2 ........
COMMIT;
if (commit_failed) { tell user to try again!; };
SQLserver will take care of the rest.
If you are trying to prevent duplicates, the simplest answer is to create a UNIQUE index on the column you want to be unique.
If you are trying to prevent more than one user from modifying the same record at the same time, your best bet is to add a last modified timestamp to the table. As you read the record to display on the screen you read the timestamp, and just before you write the changes you check the timestamp again. If it has changed, that means another user has modified the record and you should prevent the change from being written.
Without knowing how your C# code talks to the database (O/R, ADO.NET...), it's difficult to give you a useful answer...
EDIT: all the examples are great, but they won't help if he's using SubSonic for example.