I am a SQL Server database developer. We have a current requirement that we need to link our product with an existing application of a client. Our product has a SQL Server 2012 database while the client's existing application uses Oracle 11g. Since the time limit for the project completion is limited we cannot migrate our application to Oracle.
The requirement is that we have to get the customer details from the Oracle database to do billing activities in our system.
So I went through a few links and found that SQL Server linked server can be used to do this. I have successfully created a view which uses the Customer table from the Oracle database using a linked server. It will solve our problem.
Now here are my questions:
Is there any better solutions to do this other than linked server?
Are there any drawbacks when using linked server for this?
Thanks in advance
One drawback to consider is that the filtering on your view may take place at "your" end, rather than in Oracle. e.g. if you have a linked server (using, say, an OPENQUERY statement) and a view based on that and you do this:
select id from myView where id = 4711
expecting that the result will be very quick (assuming id is indexed etc.etc.), then you may be in for a shock as what will actually happen is:
the entire contents of the Oracle table are passed to SQL Server
SQL Server then filters this data, i.e. the filtering cannot be "pushed
down" into the view objects (as they are remote).
N.B.: I know there are two ways to define linked server (openquery and the other one, I forget the details), so this may not always apply, but you should be aware of the potential performance hit.
Related
We are in the process of migrating our SQL Server database to Oracle. Some business users have an Access DB with tables linked to SQL Server. Is there a way to change these connections to Oracle, and if so, is there a way to do that so the queries do not have to be updated to reflect the new source?
One of the issues I'm running into is the name of the existing linked table is DBO_TABLE1 (SQL Server connection). When I try to repoint that to Oracle, there is a different schema (let's call it SCHEMA1), so it doesn't recognize the name DBO_TABLE1.
It looks like I'd have to create new connections for each of the linked tables, which is going to be tedious because there are a lot of tables as well as many queries that will need to be modified to use the new table names.
Any help would be greatly appreciated.
I have an access 2003 database that holds all of my business data. This access database gets updated every few hours during the day.
We're currently writing a website that will need to use the data from the access database. This website (for the time being) will have only read only capabilities. Meaning there will only need to be one way transfer of data (Access -> SQL).
I'm imaging there's a way to perform this data migration from access to SQL server programatically. Does anyone have any links to something I can read about?
If this practice sounds odd, and you'd like to suggest another way to do this (or a situation where data can go both ways (Access -> SQL, SQL -> Access), that's perfectly fine.
The company is going to continue using Access 2003 for their business functionality. There's no way around that. But I'd like to build the (readonly) website on top of SQL Server.
The strategy you outlined can be very challenging. You could use INSERT queries to copy new Access rows to SQL Server, as described in another answer.
However, if you have changes to existing Access rows, and you also want those changes propagated to SQL Server, it won't be so simple. And it will be more complicated still if you want deleted Access rows deleted from SQL Server, too.
It seems more reasonable to me to use a different approach. Migrate the data to SQL Server once. Then replace the tables in your Access database with ODBC links to the SQL Server tables. Thereafter, changes to the data from within your Access application will not require a separate synchronization step ... they will already be in SQL Server. And you won't need to write any code to synchronize them.
If your concern is that the connections between the web server and SQL Server be read-only, just set them up that way. You can still independently allow read-write permissions for your Access application.
To do the initial data migration and set the SQL Server automatically, I would use the SQL Server Migration Assistant. The only thing you should definitely change that I can think of would be to turn off the Identity property on any columns that have it - to be explained below (MS Access calls Identity autonumber). Once you have your tables loaded, you can set up a dsnless connection to the database (and tables) you just created.
I haven't used the method just linked, but I believe it allows you to use SQL Server authentication to connect to the db. The benefit of using this method is you can easily change which SQL Server instance and/or database your are connecting to for development and testing.
There might be a better, automated way, but you can create several insert queries doing left joins from the primary key of the Access table to the SQL Server table, and putting a WHERE clause that specifies the SQL Server PrimaryKey must be null. This is why you need to turn off the Identity property in the SQL Server tables, so that you can insert the new data.
Finally, put the name of each query in one function, then run the function periodically.
I have used Microsoft's free SQL Server Migration Assistant (SSMA) to migrate Access to SQL Server. The tool is very simple to use. The only problem I have encountered with the tool was overloaded data types when migrating. What I mean by this is a small string will get converted to a NVARCHAR(MAX) in some instances. Otherwise, the tool is very handy and can be reused after setting up a 'profile'.
I am attempting to keep a table in Sql server updated from an access table. Any time a change is made in the access table I would like that change reflected in the sql server table. The two tables can be identical. I have created an ODBC connection from access to sql server and can export the table to sql server; I just don’t know what must be done to keep that table updated. Any suggestions are appreciated.
Should this be implemented from within Access or within sql server?
Can you just add the SQL Server table to the Access database as a linked table? (Useful article on how to add linked tables)? That way users (let's hope there's not many!) of the Access database are in effect editing the SQL Server table directly.
If this isn't desirable then how about creating another table in the SQL Server database, and adding this to the Access database as a linked table. Then, add a trigger so that when an insert/update/delete is made to this table the same operation is done on your main table.
I think setting up a Linked Server in SQL Server could be easier to implement than an automatic export of data from Access.
According to the MSDN page,
Many types OLE DB data sources can be configured as linked servers, including Microsoft Access and Excel.
Server-on-SQL-2005-Server/
Access has no "event" that occurs when a row is updated/inserted/deleted that I know of. as JeffO points out data macros that could do what you want.
You could also periodically synch them. There are several techniques to periodically do the synch task (SQL Server Agent, Windows Service, Windows Scheduler, a timer in an application etc.), but still have to deal with all the problems that exist with synchronization if both tables can be modified, the worst being data conflict resolution. There is no easy solution for that.
Perhaps if you explained the problem you have that you are solving with synching data in SQL server and Access someone might be able to point you in the direction of a solution that doesn't have these problems.
I want to save any kind of log/tables with every query executed by my application.
I know I could do this by coding it (before I make any query, I insert a new row in a log table with the query and the user who is executing it.
I have read it can be done automatically but I'm not sure how can it work with WCF Services. I mean every query is going to be executed by the same SQL user and this wouldn't be very useful for audit operations (I need to know WHO made every query, and users will be validated against my own users tables).
Have you ever had a similar scenario? Thanks in advance!
As a starting point it may be worth looking into doing this via SQL Server Profiler. You can normally find this in the Tools Menu in Management Studio.
You can set up a trace to capture all SQL run on a server. More importantly you have a myriad of filter options which can be applied so that you only capture the data you are interested in (e.g. DatabaseName, UserName).
This information can be stored directly in a SQL Table, which should give you the abillity to join onto. Of course running anything like this will result in some overhead on the SQL box.
You can try the SQL Server Audit feature. It audits singe or groups of events both on server and database level. However, be advised that the database level auditing is available in SQL Server Enterprise and Developer editions only
I have managed to get SQL Server 2005 Express up and running on my computer Ok in order to do some testing before trying this in the "Real World".
I have a fairly large MS Access 2007 Database application I need to migrate to SQL Server
retaining the "Front End" as the user interface. (The app' is already a "split" database
with a Front and Back end....)
I have done some initial testing on using SSMA to migrate my Access database To SQL
Server Express.
Clearly I don't understand some things and I thought I'd see if anyone has
any ideas.
Conceptually I thought that what needed to happen was that the Back End of the
database that resides on the server needed to be migrated to SQL server
and then the Front End re linked to the (now linked to SQL) tables in the Back End.
When I do this using SSMA I end up with renamed tables in the Back End
Access file that look something like "SSMA$myTableNameHere$local". I also
get the original table names underneath showing as ODBC linked tables.
So far so good.
BUT.... When I go to re-establish the linked tables from the FRONT END (The
user interface) all I can see is the "SSMA$myTableNameHere$local" names NOT
the original table names.(Now linked via ODBC)
I can link to the "SSMA,,,," tables but it would mean changing the names of
every table in every query and on every form and in all code on the Front
End! Not something I really want to do.
SO....
I thought I'd try to migrate the FRONT END and see what happens.
What I ended up with is a situation where, basically it works (there are
some serious errors and issues that I haven't even looked at yet... like
missing data etc.!!!!) and I still get the "SSMA$myTableNameHere$local"
tables and the ODBC linked tables with the original names.
I'm trying to understand...... Does this mean that we would do the
migration on the Front End and then just copy the same file to each user's
computer?
Another subject I'm a little confused about is that I can't link via ODBC
to SQL Server Express on the local machine (ie my computer) so I can't test
migrating the Back End and then linking to the tables via the Front End as I
have in the past in more of a client/server situation.
Assuming that SSMA replaces the tables in your back end with links to the SQL Server, all you need to do is delete the original table links in your front end and import the newly-created table links from the back end. You can then discard the back end, since it's not used for anything at all any longer.
I did transfer all my tables one by one to SQL Server 2005 fro Access DB back-end using ODBC.Instruction:
Open Access DB(back-end)
Right-click on table, you need to transfer
Scroll down drop-down box and select ODBC Databases
Select Data Source dialog box opened, Click "New" button
Create new data source dialog box opened
Scroll to the bottom and select SQL Server, Click Next
Give name to your Data Source, Click Next, Click Finish
Create New Data Source Dialog opens
Give some discription OR leave empty, Type Name of your SQL Server (you named it, when install SQL Server on your machine)
Click Next, Click Next
Check "change default database to check box
Select DB where you want your data transfer to
Click Next, Click Finish
NOTE: You need to create new DB (empty) on SQL Server, before doing all this
Now: Right-click any table, select Export, select from drop-down list ODBC, from Data Sources window select your Data Source, You created, Click OK
Use SQL Server with SQL Management Studio Express.
All dates must have a input mask; all text and Memo must have Allow Zero Length =Yes
After all disconnect all links from Access back-end, and establish links from SQL.RENAME all newly linked tables to old names. Use Fron-end user interfase, until do some new.
Forgive my lack of knowledge of Acronym Soup, but I assume SSMA is the SQL Server 2005 "import data wizard" or the wizard in Access to send the data to SQL Server. It appears that you sent the data to SQL Server from Access - something you don't want to do. You want to use the DTS in SQL Server (now called SSIS or something?) to import the data into SQL Server. Then you'll have your tables in SQL Server. Then, simply create your DSN entry for the SQL Server and re-link your tables. All should be well.
Overall, the general rule is to import Access tables using SQL Server instead of using Access to send the data to SQL Server.
I'd bite the bullet and rename the tables on the SQLServer side back to the friendly names that you had in the original database. You'll probably have less problems. Especially if you have any embedded code the MS Access side.
As far as how you will deploy the MS Access side now, it should be pretty much create the ODBC link on the user's workstation, and copy the MS Access file to their desktop (although you might want to make an MDE (or the 2007 equivalent) to prevent them from accidentally breaking it).
Frankly, now that you have migrated, you need to look at the design of your tables. It is my experience that the wizards for Access migration do a poor job of selecting the correct datatype. For instance if you had a memo field, you might easily get away with a varchar field instead but the last wizard I used (an earlier version) always converted them to text fields. Now would also be the time consider some fixes such as making date fileds datetime instead of character based if you have had that mistake in the past.
I would never consider using a wizard again to do data migration myself having experienced how very badly they can do it.
You will alos find that just converting the data to SQL Server is often not eough to really get any performance benefit. YOu will need to test all the queries and consider if you can convert them to stored procs instead if they are slow. Eliminating the translation from Jet SQL to T-sql can being performance improvements. Plus there are many features of t-sql that can imporve performance that do not have Access equivalents. Access is not big on performance tuning, but to get the benefit of performance tuning with a SQL Server backend, you need to have SQL Server specific queries written. INdexing needs to be considered if the Access tables were not indexed properly.
Using SSMA is different when you use odbc. If you have an application using fully access (back end and front end). You can manipulate objects easily bounding forms, using DAO, etc.. without problem, then when u need to migrate database to sql server u can use directly odbc (by linking yourself tables to sql server), ssma, ... the main problem how to preserve bounded forms, queries, code in the client-side.
If U use directly odbc you must relink by yourself all objects and change code but if u use ssma, you have to do nothing, you will continue to work as u did before. The problem with SSMA is how to deploy the front end to the clients if you developed client side in other place using another sql server?