I am working in a company where we have hundreds of tables and queries in MS Access and several tables in our SQL Server. Sometimes we need to combine results from both databases.
When we try to do it by linking our SQL tables to MS Access using ODBC connection, the results return very slow that causes our clients to complain. So other than non-ODBC connection property here is what I am looking for;
Being able to build a query using Sql DB and Access DB visually by dragging and dropping tables.
Being able to save these queries and re-run them using C#
Being able to use sub-queries (query in another query)
My question is if there is any kind of application or API (paid or unpaid) that supports all these terms? Or is it possible to build such a thing?
SQL Server Management Studio does all this. But running a query by trying to join a SQL server table with an access table is not a good idea and will always be slow. You need to upload the access table data to a temporary table in SQL Server and join from there.
You can use vba to import the record set to a temp table and then do a join. If you're drawing down both datasets in C# app and joining there then yes that will be relatively more efficient than joining in Access but certainly not the same thing. Joining a large Access table with another large linked table will always be slow.
Related
I have Azure SQL database database1 in server Server1.database.windows.net
I need to retrieve some records from this database, and insert them in a table in different database on different Azure server.
Do you think for this scenario it's better to do it using .Net or to use Elastic queries?
Also, is there any limitations for the elastic queries?
I have Azure SQL database database1 in server Server1.database.windows.net I need to retrieve some records from this database, and insert them in a table in different database on different Azure server. Do you think for this scenario it's better to do it using .Net or to use Elastic queries?
Your requirement is query data from one database and then insert returned data into another (different) database, in my opinion, making these operations via code in your program would completely meet your requirement, elastic query is not required for your scenario. Normally the goal of using elastic query is to facilitate querying scenarios where multiple databases contribute rows into a single overall result. You can find detailed information of the elastic query feature in this article.
Besides, sp_execute_remote can help us execute remote stored procedure calls or remote functions, which could be another approach for your scenario.
is there any limitations for the elastic queries?
Under "Preview limitations" section in this article, you can see:
Running your first elastic query can take up to a few minutes on the Standard performance tier. This time is necessary to load the elastic query functionality; loading performance improves with higher performance tiers.
Scripting of external data sources or external tables from SSMS or SSDT is not yet supported.
Import/Export for SQL DB does not yet support external data sources and external tables. If you need to use Import/Export, drop these objects before exporting and then re-create them after importing.
Elastic query currently only supports read-only access to external tables. You can, however, use full T-SQL functionality on the database where the external table is defined. This can be useful to, e.g., persist temporary results using, e.g., SELECT INTO , or to define stored procedures on the elastic query database which refer to external tables.
Except for nvarchar(max), LOB types are not supported in external table definitions. As a workaround, you can create a view on the remote database that casts the LOB type into nvarchar(max), define your external table over the view instead of the base table and then cast it back into the original LOB type in your queries.
Column statistics over external tables are currently not supported. Tables statistics are supported, but need to be created manually.
A few things about what I intend my .NET application to do:
Query various enterprise wide databases (I would not know the structure of these databases before hand, in terms of table or fields to expect)
These databases could either be Oracle or SQL Server
Have an interface where the user could select the table and the fields within, set group by and where clauses, to extract a recordset
Insert records into an Access database based on the results of the above query. I know the structure of this Access database and I have some business logic to execute before inserting the records in a certain way.
I am not sure if an ORM like NHibernate is really a solution to this requirement as I have no information before hand on the structure of data (tables, fields) that I will encounter. Is there a .NET library that will abstract the connection and querying part for me and one that works with SQL Server and Oracle.
So I have two systems I often have to join together to display certain reports. I've got one system that stores metadata on documents that is stored in SQL Server, usually by part number. The list of part numbers I would want to get documents for come from an Oracle table in our ERP system. My current method goes like this:
Get data from ERP (Oracle) system into a DataTable.
Compile string[] of part numbers from a column.
Use an IN() statement to get all document information from docs (MSSQLSVR) system into another DataTable.
Add columns to ERP DataTable, loop through rows.
Fill out document info from docs DataTable, if(erpRow["ITEMNO"] == docRow["ITEMNO"])
This, to me feels really inefficient. Now obviously I can't use one connection string to JOIN the two tables, or use a database link, so I assume there will have to be two calls, one to each database. Is there another way to join these two sets together?
I would suggest a LikedServer approach (http://msdn.microsoft.com/en-us/library/ms188279.aspx). Write a Stored Procedure on the SQL Server side that pulls the data over from an Oracle Linked Server, does the JOIN locally and returns the combined data.
SQL Server has been designed to execute JOINs efficiently. No need to try to recreate that functionality in the app layer.
Since you've ruled out a database link I would do the following
Get data from ERP (Oracle) system into a DataTable.
Pass DataTable as a Parameter to SQL Server via a Table-Valued Parameter
Return your data (no loops updating an older set)
I realize you can use the upsize wizard in access to convert this normally but as this is a server side process where we are getting the mdb files from a third party on a daily basis, I have to be able to ingest these with a no touch architecture.
Currently, I'm about to set out to write it all by hand (ugh) where I read the access database through a datasource and punch it up into sql server through bulk inserts or entity framework. I really wish there were a better way to do this though. I'm willing to entertain lots of creative methods as there are a LOT of tables and a TON of data.
There are a number of methods that come to mind, which do all indeed involve custom programming, but should be relatively simple and straightforward to implement.
From another Access DB, open the source DB programmatically (i.e., with VBA). Create linked tables to SQL backend in source DB. Copy the data from the source DB to linked table (using insert dest select * from source).
Use OPENDATASET or OPENROWSOURCE with SQL Server to directly connect to the Access DB and copy the data. You can use again insert dest select * from source to copy the data, or select * into dest from source to create a new table from the source data. This involves tweaking some system settings on sql server since it's not enabled by default, but a few google searches should get you started.
From a .NET program, use SqlBulkCopy (which is the .NET class for automating bcp) to upload data from the Access database. Just work with the data directly with ADO.Net, as there's no reason to build an entire EF layer just for migrating data from one source to another.
I have used variations of all three methods above in various projects, but for moving a large number of tables, I have found option #2 to be relatively efficient. It will involve some dynamic SQL code if your table names are dynamic on a daily basis, but if they are static, you should only have to write the logic once and use a parameter for the filename to read from.
I have two databases, one is an MS Access file, the other is a SQL Server database. I need to create a SELECT command that filters data from the SQL Server database based on the data in the Access database. What is the best way to accomplish this with ADO.NET?
Can I pull the required data from each database into two new tables. Put these in a single Dataset. Then perform another SELECT command on the Dataset to combine the data?
Additional Information:
The Access database is not permanent. The Access file to use is set at runtime by the user.
Here's a bit of background information to explain why there are two databases. My company uses a CAD program to design buildings. The program stores materials used in the CAD model in an Access database. There is one file for each model. I am writing a program that will generate costing information for each model. This is based on current material prices stored in a SQL Server database.
My Solution
I ended up just importing the data in the access db into a temporary table in the SQL server db. Performing all the necessary processing then removing the temporary table. It wasn't a pretty solution but it worked.
You don't want to pull both datasets across if you don't have to do that. You are also going to have trouble implementing Tomalak's solution since the file location may change and might not even be readily available to the server itself.
My guess is that your users set up an Access database with the people/products or whatever that they are interested in working with and that's why you need to select across the two databases. If that's the case, the Access table is probably smaller than the SQL Server table(s). Your best bet is to pull in the Access data, then use that to generate a filtered query to SQL Server so that you can minimize the data that is sent over the network.
So, the most important things are:
Filter the data ON THE SERVER so that you can minimize network traffic and also because the database is going to be faster at filtering than ADO.NET
If you have to choose a dataset to pull into your application, pull in the smaller dataset and then use that to filter the other table.
Assuming Sql Server can get to the Access databases, you could construct an OPENROWSET query across them.
SELECT a.*
FROM SqlTable
JOIN OPENROWSET(
'Microsoft.Jet.OLEDB.4.0',
'C:\Program Files\Microsoft Office\OFFICE11\SAMPLES\Northwind.mdb';'admin';'',
Orders
) as b ON
a.Id = b.Id
You would just change the path to the Access database at runtime to get to different MDBs.
First you need to do something on the server - reference the Access DB as a "Linked Server".
Then you will be able to query it from within the SQL server, pulling out or stuffing in data however you like. This web page gives a nice overview on how to do it.
http://blogs.meetandplay.com/WTilton/archive/2005/04/22/318.aspx
If I read the question correctly, you are NOT attempting to cross reference across multiple databases.
You need merely to reference details about a particular FILE, which in this case, could contain:
primary key, parent file checksum (if it is a modification), file checksum, last known author, revision number, date of last change...
And then that primary key when adding information obtained from analysing that file using your program.
If you actually do need a distributed database, perhaps you would prefer to use a non-relational database such as LDAP.
If you can't use LDAP, but must use a relational database, you might consider using GUID's to ensure that your primary keys are good.
Since you don't give enough information, i'm going to have to make some assumptions.
Assuming:
The SQL Server and the Access Database are not on the same computer
The SQL Server cannot see the Access database over a file share or it would be too difficult to achieve this.
You don't need to do joins between the access database and the sql server, only use data from teh access database as lookup elements of your where clause
If the above assumptions are correct, then you can simply use ADO to open the Access database and retrieve the data you need, possibly in a dataset or datatable. Then extract the data you need and feed it to a different ADO query to your SQL Server in a dynamic Where clause, prepared statement, or via parameters to a stored procedure.
The other solutions people are giving all assume you need to do joins on your data or otherwise execute SQL which includes both databases. To do that, you have to use linked databases, or else import the data into a table (perhaps temporary).
Have you tried benchmarking what happens if you link from the Access front end to your SQL Server via ODBC and write your SQL as though both tables are local? You could then do a trace on the server to see exactly what Jet sends to the server. You might be surprised as to how efficient Jet is with this kind of thing. If you're linking on a key field (e.g., and ID field, whether from the SQL Server or not), it would likely be the case that Jet would send a list of of the IDs. Or you could write your SQL to do it that way (using IN SELECT ... in your WHERE clause).
Basically, how efficient things will be depends on where your WHERE clause is going to be executed. If, for instance, you are joining a local Jet table with a linked SQL Server table on a single field, and filtering the results based on values in the local table, it's very likely to be extremely efficient, in that the only thing Jet will send to the server is whatever is necessary to filter the SQL Server table.
Again, though, it's going to depend entirely on exactly what you're trying to do (i.e., which fields you're filtering on). But give Jet a chance to see if it is smart, as opposed to assuming off the bat that Jet will screw it up. It may very well require some tweaking to get Jet to work efficiently, but if you can keep all your logic client-side, you're better off than trying to muck around with tracking all the Access databases from the server.