I am coding in ASP.NET C# 4. The database is SQL Server 2012.
I have a table that has 2000 rows and 10 columns. I want to load this table in memory and if the table is updated/inserted in any way, I want to refresh the in-memory copy from the DB.
I looked into SQL Server Change Tracking, and while it does what I need, it appears I have to write quite a bit of code to select from the change functions -- more coding than I want to do for a simple scenario that I have.
What is the best (simplest) solution for this problem? Do I go with CacheDependency?
I currently have a similar problem: I'm implementing a rest service that returns a table with 50+ columns and I want to cache the data on the client to reduce trafic.
I'm thinking about this implementation:
All my tables have the fields
ID AutoIncrement (primary key)
Version RowVersion (a numeric value that will be incremented
every time the record is updated)
To calculate a "fingerprint" of the table I use the select
select count(*), max(id), sum(version) from ...
Deleting records changes the first value, inserting the second value and updating the third value.
So if one of the three values changes, i have to reload the table.
Related
I am kind of stuck:
Scenario:
I have a SSIS-Package, which loads data incrementally. In the first step, I load rows from a source which have a) been inserted or b) updated into a staging table. I do this by using the last timestamp of the source table.
In the next step, I am trying to use a MERGE-Statement to update the data in another database (similar to a data warehouse). I have no control over this other database, otherwise my task would be quite easy.
Problem:
The data warehouse table includes an ID-Column ([cId], BIGINT), which it does not set by itself. I have tried to create a sequence, from which I pull a value whenever I insert a new row into the data warehouse (not when I update a row, since that row will already have an ID). However, as specified here, SQL Server will not let me use the next value from my sequence for the target of a MERGE-Statement. Since I have no control over the data warehouse, I cannot change this.
Another solution would be to get the next value from my sequence when I load the data into the staging table. This, however, will result in "holen" in my ID-sequence, because when I update a row in the data warehouse from my staging table, the [cId] column would not be updated, since that row already has an ID.
Does anyone have an idea how to solve this? I am basically trying to pull a new, unique BIGINT, whenever I do an insert inside my MERGE-Statement.
Thanks!
I am working on a project where my college wants only newly inserted or updated data. It concerns ca. 5 SQL Server tables. Values in many columns could be updated/changed (surname, id, department, exit date, residence, family status, etc)
none of these tables have timestamp or datetime column, when was last change made.
I would like to use triggers (insert and update) to get only newly inserted / updated values.
My question is, is it a good approach? If yes, should I use triggers on original tables or is it better to get data into one view and use triggers on views?
You don't have to write your own triggers and tracking tables to keep track of changing data. SQL Server Change Tracking will do that for you.
I am currently working on a phone directory application. For this application I get a flat file (csv) from corporate SAP that is updated daily that I use to update an sql database twice a day using a windows service. Additionally, users can add themselves to the database if they do not exist (ie: is not included in the SAP file). Thus, a contact can be of 2 different types: 'SAP' or 'ECOM'.
So, the Windows service downloads the file from a SAP ftp, deletes all existing contacts in the database of type 'SAP' and then adds all the contacts on the file to the database. To insert the contacts into the database (some 30k), I load them into a DataTable and then make use of SqlBulkCopy. This works particularly, running only a few seconds.
The only problem is the fact that the primary key for this table is an auto-incremented identity. This means that my contact id's grows at a rate of 60k per day. I'm still in development and my id's are in the area of 20mil:
http://localhost/CityPhone/Contact/Details/21026374
I started looking into reseeding the id column, but if I were to reseed the identity to the current highest number in the database, the following scenario would pose issues:
Windows Service Loads 30 000 contacts
User creates entry for himself (id = 30 001)
Windows Service deletes all SAP contacts, reseeds column to after current highest id: 30 002
Also, I frequently query for users based on this this id, so, I'm concerned that making use of something like a GUID instead of an auto-incremented integer will have too high a price in performance. I also tried looking into SqlBulkCopyOptions.KeepIdentity, but this won't work. I don't get any id's from SAP in the file and if I did they could easily conflict with the values of manually entered contact fields. Is there any other solution to reseeding the column that would not cause the id column values to grow at such an exponential rate?
I suggest following workflow.
import to brand new table, like tempSAPImport, with your current workflow.
Add to your table only changed rows.
Insert Into ContactDetails
(Select *
from tempSAPImport
EXCEPT
SELECT Detail1, Detail2
FROM ContactDetails)
I think your SAP table have a primary key, you can make use of the control if a row updated only.
Update ContactDetails ( XXX your update criteria)
This way you will import your data fast, also you will keep your existing identity values. According to your speed requirements, adding indexes after import will speed up your process.
If SQL Server version >= 2012 then I think the best solution for the scenario above would be using a sequence for the PK values. This way you have control over the seeding process (you can cycle values).
More details here: http://msdn.microsoft.com/en-us/library/ff878091(v=sql.110).aspx
I was working with one product where almost every table had those columns. As developers we constantly had to join to Users table to get Id of who created record and it's just a mess in a code.
I'm designing new product and thinking about this again. Does it have to be like this? Obviously, it is good to know who created record and when. But having 300+ tables reference same User table doesn't seem to be very good..
How do you handle things like this? Should I create CreatedBy column only on major entities where it's most likely needed on UI and than deal with joining? Or should I go and put it everywhere? Or maybe have another "Audit" table where I store all this and look it up only on demand(not every time entity displayed on UI)
I'm just worrying about performance aspect where every UI query will hit User table..
EDIT: This is going to be SQL Server 2008 R2 database
The problem with that approach is that you only know who created the row and who changed the row last. What if the last person to update the row was correcting the previous updater's mistake?
If you're interested in doing full auditing for compliance or accountability reasons, you should probably look into SQL Server Audit. You can dictate which tables you're auditing, can change those on the fly without having to mess with your schema, and you can write queries against this data specifically instead of mixing the auditing logic with your normal application query logic (never mind widening every row of the table itself). This will also allow you to audit SELECT queries, which other potential solutions (triggers, CDC, Change Tracking - all of which are either more work or not complete for true auditing purposes) won't let you do that.
I know that this is an older post, but one way to avoid the lookup on the user table is to de-normalize the audit fields.
So instead of a userid in the CreatedBy field you insert a username itself. This will allow for a review of the table without the user look and also allow for any changes in your user table not reflect in the audit fields. Such as deleted users.
I usually add the following to the end of a table
IsDeleted bit default 0
CreatedBy varchar(20)
CreatedOn datetime2 default getdate()
UpdatedBy varchar(20)
UpdatedOn datetime2 default getdate()
I have many tables in my database which are interrelated. I have a table (table one) which has had data inserted and the id auto increments. Once that row has an ID i want to insert this into a table (table three) with another set of ID's which comes from a form(this data will also be going into a table, so it could from from that table), the same form as the data which went into the first table came from.
The two ID's together make the primary key of the third table.
How can I do this, its to show that more than one ID is joined to a single ID for something else.
Thanks.
You can't do that through a trigger as the trigger only has available to it the data that you already inserted not data that is currenlty only residing in your user interface.
Normally how you handle this situation is that you write a stored proc that inserts the meeting, returns the id value (using scope_identity() in SQL Server, but I'm sure other databases would have method to return the auto-generated id as well). Then you would use that value to insert to the other table with the other values you need for that table. You would of course want to wrap the whole thing in a transaction.
I think you can probably do what you're describing (just write the INSERTs to table 3) in the table 1 trigger) but you'll have to put the additional info for the table 3 rows into your table 1 row, which isn't very smart.
I can't see why you would do that instead of writing the INSERTs in your code, where someone reading it can see what's happening.
The trouble with triggers is that they make it easy to hide business logic in the database. I think (and I believe I'm in the majority here) that it's easier to understand, manage, maintain and generally all-round deal with an application where all the business rules exist in the same general area.
There are reasons to use triggers (for propagating denormalised values, for example) just as there are reasons for useing stored procedures. I'm going to assert that they are largely related to performance-critical areas. Or should be.