I have an auditing trigger that automatically places the time something was updated and the user that updated in fields in all my tables. I have another set of triggers that write event information from updates to an events table. The issue is when someone updates something, the event information is fired twice because of the first triggers. How to I suppress the duplicate entries?
Look into TRIGGER_NESTLEVEL function. It returns the current level of trigger nesting. You can check that to prevent the duplicates.
I guess you have 2 choices:
Either combine both sets of triggers into one.
Or, there is a per database setting that allows recursive firing of triggers to be disabled.
You can also turn off nested triggers all together, if you have enough permissions (some webhosts don't allow you to do this). There is a stored procedure (Sql 2005) called sp_configure that lets you modify the server's configuration. The statement below disables nested triggers, which will stop a trigger from firing another trigger.
exec sp_configure 'nested triggers', 0
Disabling trigger-fires-trigger behavior can also be done in SS2005 by going into SS Mgt Studio and selecting the icon of the server in question, right-clicking, then select "Properties". Then select "Advanced" from the list on the left and set the value for "Allow Triggers to Fire Others" to 'False'.
Related
Using MS SQL Server, a Trigger calls a Stored Procedure which internally makes a select, will the return values be the new or old ones?
I know that inside the trigger I can access them by FROM INSERTED i inner join DELETED, but in this case I want to reuse (cannot change it) an existing Stored Procedure that internally makes a select on the triggered table and processes some logic with them. I just want to know if I can be sure that the existing logic will work or not (by accessing the NEW values).
I can simply try to simulate it with one update... But maybe there are other cases (example: using transactions or something else) that I maybe not be aware and never test it that could result in a different case.
I decided to ask someone else that might know better. Thank you.
AFTER triggers (the default) fire after the DML action. When the proc is called within the trigger, the tables will reflect changes made by the statement that fired the trigger as well changes made within the trigger before calling the proc.
Note changes are uncommitted until the trigger completes or explict transaction later committed.
Since the procedure is running in the same transaction as the (presumably, "after") trigger, it will see the uncommitted data.
I hope you see the implications of that: the trigger is executing as part of the transaction started by the DML statement that caused it to fire, so the stored procedure is part of the same transaction, so a "complicated" stored procedure means that transaction stays open longer, holding locks longer, making responses back to users slower, etc etc.
Also, you said
internally makes a select on the triggered table and processes some logic with them.
if you just mean that the procedure is selecting the data in order to do some complex processing and then write it to somewhere else inside the database, ok, that's not great (for reasons given above), but it will "work".
But just in case you mean you are doing some work on the data in the procedure and then returning that back to the client application, Don't do that
The ability to return results from triggers will be removed in a future version of SQL Server. Triggers that return result sets may cause unexpected behavior in applications that aren't designed to work with them. Avoid returning result sets from triggers in new development work, and plan to modify applications that currently do. To prevent triggers from returning result sets, set the disallow results from triggers option to 1.
The database I'm working on has a trigger which calls a stored procedure which takes 42 seconds to run if I do an UPDATE using T-SQL. If I edit the row in SQL Server Management Studio, the row updates instantly. Triggers are executed in the edit window as well as on T-SQL UPDATES, aren't they?
The SQL code in the stored procedure comes back instantly if I run it directly or call it using EXEC, the only circumstances when it runs slowly are when the trigger is called by an UPDATE statement.
It depends how the trigger was set up, Triggers will only run on Update, Delete and Insert statements (Depending which of the three are chosen) On the table it is set against.
Could you give the code used to create the trigger?
These triggers run after an insert, update or delete on a table
click here for details about different type of triggers and demo for triggers
Do you know how to obtain the text of sql statement inside a trigger?
Thanks
Sorry to be the bearer of sad tidings, but I don't believe you can do that. No triggering event I'm aware of has visibility on the SQL statement text. The triggering events supported by Oracle (11g) are:
An INSERT, UPDATE, or DELETE statement on a specific table (or view, in some cases)
A CREATE, ALTER, or DROP statement on any schema object
A database startup or instance shutdown
A specific error message or any error message
A user logon or logoff
None of these, as far as I'm aware, have access to the text of the SQL statement. Docs here
I have a problem to solve which requires undo operation of each executed sql file in Oracle Database.
I execute them in an xml file with MSBuild - exec command sqlplus with log in and #*.sql.
Obviously rollback won't do, because it can't rollback already commited transaction.
I have been searching for several days and still can't find the answer. What I learned is Oracle Flashback and Point in Time Recovery. The problem is that I want the changes to be undone only for the current user i.e. if another user makes some changes at the same time then my solution performs undo only on user 'X' not 'Y'.
I found the start_scn and commit_scn in flashback_transaction_query. But does it identify only one user? What if I flashback to a given SCN? Will that undo only for me or for other users as well? I have taken out
select start_scn from flashback_transaction_query WHERE logon_user='MY_USER_NAME'
and
WHERE table_name = "MY_TABLE NAME"
and performed
FLASHBACK TO SCN"here its number"
on a chosen operation's SCN. Will that work for me?
I also found out about Point in Time Recovery but as I read it makes the whole database unavailable so other users will be unable to work with it.
So I need something that will undo a whole *.sql file.
This is possible but maybe not with the tools that you use. sqlplus can rollback your transaction, you just have to make sure auto commit isn't enabled and that your scripts only contain a single commit right before you end the sqlplus session (if you don't commit at all, sqlplus will always roll back all changes when it exits).
The problems start when you have several scripts and you want, for example, to rollback a script that you ran yesterday. This is a whole new can of worms and there is no general solution that will always work (it's part of the "merge problem" group of problems, i.e. how can you merge transactions by different users when everyone can keep transactions open for as long as they like).
It can be done but you need to carefully design your database for it, the business rules must be OK with it, etc.
To general approach would be to have a table which contains the information which rows were modified (= created,updated,deleted) by the script plus the script name plus the time when it was executed.
With this information, you can generate SQL which can undo the changes created by a script. To fill such a table, use triggers or generate your scripts in such a way that they write this information as well (note: This is probably beyond a "simple" sqlplus solution; you will have to write your own data loader for this).
Ok I solved the problem by creating a DDL and DML TRIGGER. The first one takes "extra" column (which is the DDL statement you have just entered) from v$open_cursor and inserts into my table. The second gets "undo_sql" from flashback_transaction_query which is the opposite action of your DML action - if INSERT then undo_sql is DELETE with all necessary data.
Triggers work before DELETE,INSERT (DML) on specific table and ALTER,DROP,CREATE (DDL) on specific SCHEMA or VIEW.
I have table with update cursor which do not allow me to do bulk updates on it, but need to do some periodical bulk updates (query in sql job). To do this I want to disable cursor in code (disabling trigger in SSMS can ends with timeout error), but when disabling in query runs until I stop it.
Can I somehow set timeout for disabling trigger in query code (or set timeout for job run)?
Thanks
Another option might be to use CONTEXT_INFO. This allows you to set a sort of global variable that is scoped to the current request. Before executing the bulk update you can set the CONTEXT_INFO to a specific value. The trigger can check for this value and skip execution. This way you don't have to disable the trigger.
You could make disabling and re-enabling the trigger part of the transaction. Then if the update query times out, the disabling of the trigger will be rolled back too.