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
Related
Good day,
I run many databases under interbase XE7 and 2017 now.
Lately, I got a strange behavior on one of the db:
A table with a primary key was found hosting many rows with similar values, like image below.
We can see that SCRIPTTYPE is a primary key column and it contains many times MATRIX, no space or strange characters ( I checked).
I was able to backup / restore without issues.
I am puzzled by this and I am wondering if anybody did encountered something similar?
And how it was done?
Thanks.
enter image description here
Run this query to be sure:
select SCRIPTTYPE, count(*)
from yourtable
group by SCRIPTTYPE
order by 2 desc
If you get a count>1, then I'd argue it's simple a bug and you should contact support. For them to assist you they'll almost certainly need your database, so you should be prepared to provide that. Based on your description, you should be able to drop all tables except the one, and drop all fields except your key, then backup and restore to get the simplest test case.
I have a table in db2 which is having a varchar column. I want to insert only lower case string in the column.
Is it possible to change the case to lower whenever an insertion happens in that column. What will be the alter
Query for that if possible ?
I can not make another column which can take reference of my current column and be referenced like ucase(Current_column)
The means to ensure the effect of lower-casing the data that is inserted into a column, i.e. "to change the case to lower whenever an insertion happens in that column", is a TRIGGER.
Presumably much like Why is my “before update” trigger changing unexpected columns?, per having noted in a followup comment to the OP that "I tried making a BEFORE INSERT", a TRIGGER similar to the following apparently was implemented in that attempt?:
CREATE TRIGGER TOLOWER_BI BEFORE INSERT ON USERS
REFERENCING NEW AS N OLD AS O FOR EACH ROW MODE DB2ROW
set N.LoginId= lcase(N.LoginId)
If so, then "the application is not picking the trigger" [also from a followup comment to the OP] must be explained, because a TRIGGER is in effect at the database layer, such that an application has no choice [no picking] with regard to the effects of the trigger being enforced.
Hopefully an easy question for someone with more experience than me. I have a stored procedure that Inserts records into a table. Like all databases that I have worked with, when you insert a record it inserts it into the bottom of the table. I would like to insert it to the top of the table and then move all the existing records down by one (I assume this would happen automatically with the insert).
I want to to do this because I'm using the 'Top #' keyword. I am pretty sure that I could just leave it the way it is, and instead of using the 'Top" keyword, I could use the 'Bottom" keyword. But I want to make it easier for people reading it that aren't familiar with it, so they can instantly see the newest entries. I'm going to keep researching this on my own, but If someone knew off the top of their head and could save me the time that would be appreciated.
is there any incremental id on that table.If yes then create clustered index on that id with descending order
this is my first time using SQL at all, so this might sound basic. I'm making an iPhone app that creates and uses a sqlite3 database (I'm using the libsqlite3.dylib database as well as importing "sqlite3.h"). I've been able to correctly created the database and a table in it, but now I need to know the best way to get stuff back from it.
How would I go about retrieving all the information in the table? It's very important that I be able to access each row in the order that it is in the table. What I want to do (if this helps) is get all the info from the various fields in a single row, put all that into one object, and then store the object in an array, and then do the same for the next row, and the next, etc. At the end, I should have an array with the same number of elements as I have rows in my sql table. Thank you.
My SQL is rusty, but I think you can use SELECT * FROM myTable and then iterate through the results. You can also use a LIMIT/OFFSET(1) structure if you do not want to retrieve all elements at one from your table (for example due to memory concerns).
(1) Note that this can perform unexpectedly bad, depending on your use case. Look here for more info...
How would I go about retrieving all the information in the table? It's
very important that I be able to access each row in the order that it
is in the table.
That is not how SQL works. Rows are not kept in the table in a specific order as far as SQL is concerned. The order of rows returned by a query is determined by the ORDER BY clause in the query, e.g. ORDER BY DateCreated, or ORDER BY Price.
But SQLite has a rowid virtual column that can be used for this purpose. It reflects the sequence in which the rows were inserted. Except that it might change with a VACUUM. If you make it an INTEGER PRIMARY KEY it should stay constant.
order by rowid
I have a (very simple and standard) UPDATE statement which works fine either directly in Query Analyser, or executed as a stored procedure in Query Analyser.
UPDATE A
SET
A.field1 = B.col1
, A.field2 = B.col2
FROM
tblA AS A INNER JOIN tblB AS B
ON A.pk1 = B.pk1 AND A.pk2 = B.pk2
Problem is when i execute the same stored proc via microsoft ADP (by double-clicking on the sproc name or using the Run option), it says "query ran successfully but did not return records" AND does NOT update the records when i inspect the tables directly.
Before anyone even says "syntax of MS-Access is different than SQLServer T-SQL", remember that with ADP everything happens on the server and one is actually passing thru to T-SQL.
Any bright ideas from any ADP gurus out there?
Gotcha. Responding to my own question for the benefit of anyone else.
Tools / Options / Advanced / Client-Server Settings / Default max records is set at 10,000 (presumably this is the default). Change this to 0 for unlimited.
My table had 100,000+ rows and whatever set of 10,000 it was updating was difficult to find ( among a sea of 90,000+ un-updated rows ). Hence the update did not work fully as expected.
Try and see whether the query gets executed on the SQL Server using SQL profiler.
Also, I think you might need to close the linked table & re-open it to see the updated records.
Does that work?
Run the query with SQL PRofiler running. Before you start the trace add in all the error events. This will give you any errors that the SQL Server is generating that the Access ADP might not be showing correctly (or at all).
Feel free to post them here.
Just as a reference, here's a paper I wrote on Update Queries that discusses some of the issues associated with when the fail.
http://www.fmsinc.com/microsoftaccess/query/snytax/update-query.html
I seem to remember that I always got the "didn't return any rows" message and had to simply turn off the messaging. It's because it isn't returning any rows!
as for the other - sometimes there's a primary key issue. Does the table being updated have a primary key in SQLServer? If so, check the view of the table in Access - sometimes that link doesn't come through. It's been a while, so I could be wrong, but I think you may need to look at the design view of the table while in access and add the primary key there.
EDIT: Additional thought:
in your debugging, try throwing in print statements to see what the values of your inputs are. Is it actually picking up the data from the table as you expect when you execute from access?