Is there a quick way to find out when last change took place in some table?
EDIT:
I realize that i can add a column which will hold a change date, but i am wondering if there is some kind of metadata that can be accessed by EF. My db is hosted on SQL Server 2008.
Add a 'last updated' column to your table and query that one for the latest change.
Update: If that is not an option as per the update to the question, you could:
a) create a separate db table with table name and date/time and update that one with triggers on the table you want to track.
...or...
b) since you're using SQL Server 2008 you could possibly do something with SQL Server change tracking. There's no built-in support for change tracking in EF, but that doesn't prevent you from using it 'on the side'...
Related
I use SQL Server with ASP.NET Core and EF Core. After each record is added, the identity column's value jumps about by 1000 and creates a gap between current row and the last previously added row.
Questions
Is there any way to prevent this?
How to delete those gaps that have been created before?
If I use GUID for key columns to prevent that issue, is there a problem (performance or each other problem)?
Is it way on the server side that with EF Core could handle it (each some way)?
Thank you in advance for your helps...
For the reason for 1000-value gaps, see Aaron Bertrand's answer
It doesn't really make sense to "want" to delete the gaps. The content of an identity column contains no semantic information. It correlates to nothing "in the world" outside the database. The gaps are as meaningless as the values themselves.
I don't see how a uniqueidentifier would "prevent" that issue. A uniqueidentifier may be "meaningfully" sortable (if you use newsequentialid()), but there's no sense in which any particular value is "one more" than a previous value.
You can certainly try to build your own key generating algorithm that does not produce gaps, but you will run into concurrency issues (also mentioned by Mr Bertrand).
workaround trick:
CREATE OR ALTER TRIGGER TGR_Transaction_Identity_Fix
ON [dbo].[TBL_Transaction]
FOR INSERT
AS
BEGIN
DECLARE #RESEEDVAL INT
SELECT #RESEEDVAL = MAX(TransactionId) FROM [dbo].[TBL_Transaction]
DBCC CHECKIDENT([TBL_Transaction], RESEED, #RESEEDVAL)
END
this triger will reset identity on each insert
I am relatively new to Oracle 12C, I have question about default settings. What I want actually whenever inserting new data in db to be saved in upper case regardless how was entered in initial query. How to change settings to accomplish this?
You can create a trigger that upon any insert statement will fire a function to convert the entire column to uppercase.
UPDATE
Customers
SET
FirstName = UPPER(FirstName)
I've been tasked with finding a way to migrate data into a DB2 AS400 database. When the data is entered (currently manually) on the front end, the system is doing some calculations and inserting the results in a table.
My understanding is that it's using a trigger to do so. I don't know very much about this stuff, but I have written code to directly insert values into that same table. Is there a way for me to figure out what trigger is being fired when users enter data manually?
I've looked in QSYS2/SYSTRIGGERS and besides not making much sense to me, I see no triggers that belong to the SCHEMA with my table in it.
Any help here would be awesome, as I am stuck.
SELECT *
FROM QSYS2.SYSTRIGGERS
WHERE TABSCHEMA = 'MYSCHEMA'
AND TABNAME = 'MYTABLE'
Should work fine.
If you'd prefer to use a 5250 command line, the Display File Description (DSPFD) command will show you the triggers on a file (table)
DSPFD FILE(MYSCHMA/MYTABLE) TYPE(*TRG)
Lastly, trigger information is available via the IBM i Navigator GUI. Either the older fat client version or the newer web based one.
I'm interested in using the following audit mechanism in an existing PostgreSQL database.
http://wiki.postgresql.org/wiki/Audit_trigger
but, would like (if possible) to make one modification. I would also like to log the primary_key's value where it could be queried later. So, I would like to add a field named something like "record_id" to the "logged_actions" table. The problem is that every table in the existing database has a different primary key fieldname. The good news is that the database has a very consistent naming convention. It's always, _id. So, if a table was named "employee", the primary key is "employee_id".
Is there anyway to do this? basically, I need something like OLD.FieldByName(x) or OLD[x] to get value out of the id field to put into the record_id field in the new audit record.
I do understand that I could just create a separate, custom trigger for each table that I want to keep track of, but it would be nice to have it be generic.
edit: I also understand that the key value does get logged in either the old/new data fields. But, what I would like would be to make querying for the history easier and more efficient. In other words,
select * from audit.logged_actions where table_name = 'xxxx' and record_id = 12345;
another edit: I'm using PostgreSQL 9.1
Thanks!
You didn't mention your version of PostgreSQL, which is very important when writing answers to questions like this.
If you're running PostgreSQL 9.0 or newer (or able to upgrade) you can use this approach as documented by Pavel:
http://okbob.blogspot.com/2009/10/dynamic-access-to-record-fields-in.html
In general, what you want is to reference a dynamically named field in a record-typed PL/PgSQL variable like 'NEW' or 'OLD'. This has historically been annoyingly hard, and is still awkward but is at least possible in 9.0.
Your other alternative - which may be simpler - is to write your audit triggers in plperlu, where dynamic field references are trivial.
Can any one help me why this error occurs when i update using sqlDataadapter with join query
Dynamic SQL generation is not supported against multiple base tables.
You have a "join" in your main query for your dataset (The first one in the TableAdapter with a check by it). You can't automatically generate insert/update/delete logic for a TableAdapter when the main query has multiple tables referenced in the query via a join. The designer isn't smart enough to figure out which table you want to send updates to in that case, that is why you get the error message.
Solution. Ensure that your main query only references the table you want the designer to write insert/update/delete code for. Your secondary queries may reference as many tables as you want.
It was in the case that i was trying to set value for identity column in my datarow. Simply i deleted the code to set value for identity column and it will work.
My Scenario:
Database:
uin [primary, identity]
name
address
Whenever i tried to set the datarow("uin") the error occurs. But works fine with datarow("name") and datarow("address").
Hope it works for you too