I am struggling to find an simple solution to import a table that has a "before insert" trigger. When importing the table, the trigger fires at each row that is imported, wreaking havoc in the table.
That trigger is supposed to create an incremental unique ID each time we create a new row (it is an idea of the type "yy_mm_dd".incremental_integer_for_the_day, and I have found no other way to get MariaDB to create it).
Is there a better way than deleting the trigger in both the exporting and receiving databases, doing the import, and then recreating manually the trigger???
Thanks!
E.
Many thanks!
Yes, it does work if I manually edit the export file, to move the creation triggers after the insertion of the rows, leaving the drop trigger where it is (i.e. before the rows to import). So that is a solution, although it does require some manual edit with my SQL software (Querious) which generates an export script with the triggers at the beginning.
And your suggestion to create two columns, one with the date and the other with the increment may be one to explore. Although since I have to reset the increment each period (day in my example), it would still require another trigger, or some PHP code.
What I wanted to avoid with the trigger was the sql request to retrieve the max(ID), increment it (or in your second solution the max(date) and the max(id in the period), check if first row of day, then reset to 1 or increment) and another request to save the ID value...
There does not seem to be a way to disable the triggers during the import, as there is to disable the foreign key check.
E.
Related
This is probably laughably easy for an SQL expert, but SQL (although I can use it) is not really my thing.
I've got a table in a DB. (Let's call it COMPUTERS)
About 10.000 rows. 25 columns. 1 unique key: Column ASSETS.
Occasionally an external program will delete 1 or more of the rows, but isn't supposed to do that, because we still need to know some info from those rows before we can really delete the items.
We can't control the behavior of the external application so we came up with a different idea:
We want to create a second identical table (COMPUTERS_BACKUP) and initially fill this with a one-on-one copy of COMPUTERS.
After that, once a day copy new records from COMPUTERS to COMPUTERS_BACKUP and update those records in COMPUTERS_BACKUP where the original in COMPUTERS has changed (ASSETS column will never change).
That way we keep the last state of a record deleted from COMPUTERS.
Can someone supply the code for a stored procedure that can be scheduled to run once a day? I can probably figure this out myself, but it would take me several hours or so and I'm very pressed for time.
just create a trigger for insert computers table
CREATE TRIGGER newComputer
ON [Computers]
AFTER INSERT
Begin
INSERT INTO COMPUTERS_BACKUP
SELECT * FROM Inserted
End
It'll work when you insert new computer to computers table and it'll also insert the record to bakcup table
When you update computers you could change computers backup too with update trigger
CREATE TRIGGER newComputer
ON [Computers]
AFTER UPDATE
Begin
//can access before updating the record through SELECT * FROM Deleted
//can access after updating the record through SELECT * FROM Inserted
UPDATE Computers_BACKUP SET
(attributes) = inserted.(attribute)
WHERE id = inserted.id
End
At the end I guess you don't want to delete the backup when original record is deleted from computers table. You can chech more examples from msdn using triggers.
When a record removed from computers table
CREATE TRIGGER computerDeleted ON [Computers] AFTER DELETE
Begin
INSERT INTO Computers_BACKUP
SELECT * FROM Deleted
End
Besides creating triggers, you may look into enabling Change Data Capture, which is available in SQL Server Enterprise Edition. It may be an overshot, but it should be mentioned and you may find it useful for other tables and objects.
IMHO a possible solution, if you never delete records (only update) from that table in your application, can be to introduce an INSTEAD OF DELETE trigger
CREATE TRIGGER tg_computers_delete ON computers
INSTEAD OF DELETE AS
DELETE computers WHERE 1=2;
It will prevent the deletion of the records.
Here is SQLFiddle demo.
A trigger for Before Delete event can help you to guard this table:
CREATE TRIGGER backup_row_before_delete ON COMPUTERS_Table FOR Delete
as
INSERT INTO Computers_Backup
SELECT deleted.* from deleted
You can change deleted.* for deleted.col1, deleted.col2 if you want to keep certain columns only.
will delete 1 or more of the rows, but isn't supposed to do that
Then you have permission and integrity issues.
You can most certainly use a trigger to record deletions (and updates of course) but I would not recommend you use it purely to keep a copy of stuff you didn't want deleted in the first place!
Remove delete permissions if you have to or beef up your data integrity if you can. Without your schema it's hard to tell exactly how though.
Finally, use your (INSTEAD OF) trigger to check whatever conditions you need to prevent the delete when appropriate.
At work we have a table to hold settings which essentially contains the following columns:
PARAMNAME
VALUE
Most of the time new settings are added but on rare occasions, settings are removed. Unfortunately this means that any scripts which might have previously updated this value will continue to do so despite the fact that the update results in "0 rows updated" and leads to unexpected behaviour.
This situation was picked up recently by a regression test failure but only after much investigation into why the data in the system was different.
So my question is: Is there a way to generate an error condition when an update results in zero rows updated?
Here are some options I have thought of, but none of them are really all that desirable:
PL/SQL wrapper which notices the failed update and throws an exception.
Not ideal as it doesn't stop anyone/a script from manually doing an update.
A trigger on the table which throws an exception.
Goes against our current policy of phasing out triggers.
Requires updating trigger every time a setting is removed and maintaining a list of obsolete settings (if doing exclusion).
Might have problems with mutating table (if doing inclusion by querying what settings currently exist).
A PL/SQL wrapper seems like the best option to me. Triggers are a great thing to phase out, with the exception of generating sequences and inserting history records.
If you're concerned about someone manually updating rather than using the PL/SQL wrapper, just restrict the user role so that it does not have UPDATE privileges on the table but has EXECUTE privileges on the procedure.
Not really a solution but a method to organize things a bit:
Create a separate table with the parameter definitions and link to that table from the parameter value table. Make the reference to the parameter definition required (nulls not allowed).
Definition table PARAMS (ID, NAME)
Actual settings table PARAM_VALUES (PARAM_ID, VALUE)
(changing your table structure is also a very effective way to evoke errors in scripts that have not been updated...)
May be you can use MERGE statement
here is a link for it
http://www.oracle-developer.net/display.php?id=203
The merge statement allows you to combine insert and update in the same query, so in case the desired row does not exist you may insert a record in a buffer table to indicate the the row does not exist or else you can update the required record
Hope it helps
I'm trying to add a simple trigger to a table- the 1st issue i came accross was that this table has text columns - so the for delete, insert, update triggers aren't going to float. 'instead of' does though.
I am now up against the fact that the table has cascades set on it. Do you know if there's a way to get around that little gem or am I basically fubared?
Create a new table, which everyone uses instead of the cascading table. Then build your "instead of" trigger onto the new table, and update the old table within the trigger.
The old table will cascade as normal, but your new table doesn't have any cascades.
UPDATE:
You could try adding a view rather that creating another table. You could even exclude those text columns from the view.
I don't know what version of SQL Server you are on but text columns are deprecated - they will NOT be in the next version of SQL Server. If you are on any version higher than 2000, I would suggest you make it an immediate prioroity to fix those by making them nvarchar(max) (You will also need to change code that uses CONTAINS, WRITETEXT and other text type code).
That said, I always got the value of text column in a trigger by joining inserted to the actual table itself on the primary key.
I'm not sure what to do about your cascade question as we do not allow cascade delete or update for performance reasons. As far as I can tell triggers will still fire (and should definitely be written to handle multiple record inserts, updates or deletes, but I strongly feel all triggers should be written this way). What problem exactly are you running into with the cascades?
This question is very similar to SQL Server 2005: T-SQL to temporarily disable a trigger
However I do not want to disable all triggers and not even for a batch of commands, but just for one single INSERT.
I have to deal with a shop system where the original author put some application logic into a trigger (bad idea!). That application logic works fine as long as you don't try to insert data in another way than the original "administration frontend". My job is to write an "import from staging system" tool, so I have all data ready. When I try to insert it, the trigger overwrites the existing Product Code (not the IDENTITY numeric ID!) with a generated one. To generate the Code it uses the autogenerated ID of an insert to another table, so that I can't even work with the ##IDENTITY to find my just inserted column and UPDATE the inserted row with the actual Product Code.
Any way that I can go to avoid extremly awkward code (INSERT some random characters into the product name and then try to find the row with the random characters to update it).
So: Is there a way to disable triggers (even just one) for just one INSERT?
You may find this helpful:
Disabling a Trigger for a Specific SQL Statement or Session
But there is another problem that you may face as well.
If I understand the situation you are in correctly, your system by default inserts product code automatically(by generating the value).
Now you need to insert a product that was created by some staging system, and for that product its product code was created by the staging system and you want to insert it to the live system manually.
If you really have to do it you need to make sure that the codes generated by you live application in the future are not going to conflict with the code that you inserted manually - I assume they musty be unique.
Other approach is to allow the system to generate the new code and overwrite any corresponding data if needed.
You can disable triggers on a table using:
ALTER TABLE MyTable DISABLE TRIGGER ALL
But that would do it for all sessions, not just your current connection.. which is obviously a very bad thing to do :-)
The best way would be to alter the trigger itself so it makes the decision if it needs to run, whether that be with an "insert type" flag on the table or some other means if you are already storing a type of some sort.
Rather than disabling triggers can you not change the behaviour of the trigger. Add a new nullable column to the table in question called "insertedFromImport".
In the trigger change the code so that the offending bit of the trigger only runs on rows where "insertedFromImport" is null. When you insert your records set "insertedFromImport" to something non-null.
Disable the trigger, insert, commit.
SET IDENTITY_INSERT Test ON
GO
BEGIN TRAN
DISABLE TRIGGER trg_Test ON Test
INSERT INTO Test (MyId, MyField)
VALUES (999, 'foo')
ENABLE TRIGGER trg_Test ON Test
COMMIT TRAN
SET IDENTITY_INSERT Test OFF
GO
Can you check for SUSER_SNAME() and only run when in context of the administration frontend?
I see many things that could create a problem. First change the trigger to consider multiple record imports. That may probably fix your problem. DO not turn off the trigger as it is turned off for everyone not just you. If you must then put the database into single user user mode before you do it and do your task during off hours.
Next, do not under any circumstances ever use ##identity to get the value just inserted! USe scope_identity instead. ##identity will return the wrong value if there are triggers onthe table that also do inserts to other tables with identity fields. If you are using ##identity right now through your system (since we know your system has triggers), your abosolute first priority must be to immediately find and change all instances of ##identity in your code. You can have serious data integrity issues if you do not. This is a "stop all work until this is fixed" kind of problem.
As far as getting the information you just inserted back, consider creating a batchid as part of you insert and then adding a column called batchid (which is nullable so it won't affect other inserts)to the table. Then you can call back what you inserted by batchid.
If you insert using BULK INSERT, you can disable triggers just for the insert.
I'm pretty sure bulk insert will require a data file on the file system to import so you can't just use T-SQL.
To use BULK INSERT you need INSERT and ADMINISTRATOR BULK OPERATION permissions.
If you disable triggers or constraints, you'll also need ALTER TABLE permission.
If you are using windows authentication, your windows user will need read access from the file. if using Mixed Mode authentication, the SQl Server Service account needs read access from the file.
When importing using BULK IMPORT, triggers are disabled by default.
More information: http://msdn.microsoft.com/en-us/library/ms188365.aspx
On our live/production database I'm trying to add a trigger to a table, but have been unsuccessful. I have tried a few times, but it has taken more than 30 minutes for the create trigger statement to complete and I've cancelled it.
The table is one that gets read/written to often by a couple different processes. I have disabled the scheduled jobs that update the table and attempted at times when there is less activity on the table, but I'm not able to stop everything that accesses the table.
I do not believe there is a problem with the create trigger statement itself. The create trigger statement was successful and quick in a test environment, and the trigger works correctly when rows are inserted/updated to the table. Although when I created the trigger on the test database there was no load on the table and it had considerably less rows, which is different than on the live/production database (100 vs. 13,000,000+).
Here is the create trigger statement that I'm trying to run
CREATE TRIGGER [OnItem_Updated]
ON [Item]
AFTER UPDATE
AS
BEGIN
SET NOCOUNT ON;
IF update(State)
BEGIN
/* do some stuff including for each row updated call a stored
procedure that increments a value in table based on the
UserId of the updated row */
END
END
Can there be issues with creating a trigger on a table while rows are being updated or if it has many rows?
In SQLServer triggers are created enabled by default. Is it possible to create the trigger disabled by default?
Any other ideas?
The problem may not be in the table itself, but in the system tables that have to be updated in order to create the trigger. If you're doing any other kind of DDL as part of your normal processes they could be holding it up.
Use sp_who to find out where the block is coming from then investigate from there.
I believe the CREATE Trigger will attempt to put a lock on the entire table.
If you have a lots of activity on that table it might have to wait a long time and you could be creating a deadlock.
For any schema changes you should really get everyone of the database.
That said it is tempting to put in "small" changes with active connections. You should take a look at the locks / connections to see where the lock contention is.
That's odd. An AFTER UPDATE trigger shouldn't need to check existing rows in the table. I suppose it's possible that you aren't able to obtain a lock on the table to add the trigger.
You might try creating a trigger that basically does nothing. If you can't create that, then it's a locking issue. If you can, then you could disable that trigger, add your intended code to the body, and enable it. (I do not believe you can disable a trigger during creation.)
Part of the problem may also be the trigger itself. Could your trigger accidentally be updating all rows of the table? There is a big differnce between 100 rows in a test database and 13,000,000. It is a very bad idea to develop code against such a small set when you have such a large dataset as you can have no way to predict performance. SQL that works fine for 100 records can completely lock up a system with millions for hours. You really want to know that in dev, not when you promote to prod.
Calling a stored proc in a trigger is usually a very bad choice. It also means that you have to loop through records which is an even worse choice in a trigger. Triggers must alawys account for multiple record inserts/updates or deletes. If someone inserts 100,000 rows (not unlikely if you have 13,000,000 records), then looping through a record based stored proc could take hours, lock the entire table and cause all users to want to hunt down the developer and kill (or at least maim) him because they cannot get their work done.
I would not even consider putting this trigger on prod until you test against a record set simliar in size to prod.
My friend Dennis wrote this article that illustrates why testing a small volumn of information when you have a large volumn of information can create difficulties on prd that you didn't notice on dev:
http://blogs.lessthandot.com/index.php/DataMgmt/?blog=3&title=your-testbed-has-to-have-the-same-volume&disp=single&more=1&c=1&tb=1&pb=1#c1210
Run DISABLE TRIGGER triggername ON tablename before altering the trigger, then reenable it with ENABLE TRIGGER triggername ON tablename