We recently migrated a large DB2 database to a new server. It got trimmed a lot in the migration, for instance 10 years of data chopped down to 3, to name a few. But now I find that I need certain data from the old server until after tax season.
How can I run a UNION query in DBeaver that pulls data from two different connections..? What's the proper syntax of the table identifiers in the FROM and JOIN keywords..?
I use DBeaver for my regular SQL work, and I cannot determine how to span a UNION query across two different connections. However, I also use Microsoft Access, and I easily did it there with two Pass-Through queries that are fed to a native Microsoft Access union query.
But how to do it in DBeaver..? I can't understand how to use two connections at the same time.
For instance, here are my connections:
And I need something like this...
SELECT *
FROM ASP7.F_CERTOB.LDHIST
UNION
SELECT *
FROM OLD.VIPDTAB.LDHIST
...but I get the following error, to which I say "No kidding! That's what I want!", lol... =-)
SQL Error [56023]: [SQL0512] Statement references objects in multiple databases.
How can this be done..?
This is not a feature of DBeaver. DBeaver can only access the data that the DB gives it, and this is restricted to a single connection at a time (save for import/export operations). This feature is being considered for development, so keep an eye out for this answer to be outdated sometime in 2019.
You can export data from your OLD database and import it into ASP7 using DBeaver (although vendor tools for this are typically more efficient for this). Then you can do your union as suggested.
Many RDBMS offer a way to logically access foreign databases as if they were local, in which case DBeaver would then be able to access the data from the OLD database (as far as DBeaver is concerned in this situation, all the data is coming from a single connection). In Postgres, for example, one can use a foreign data wrapper to access foreign data.
I'm not familiar with DB2, but a quick Google search suggests that you can set up foreign connections within DB2 using nicknames or three-part-names.
If you check this github issue:
https://github.com/dbeaver/dbeaver/issues/3605
The way to solve this is to create a task and execute it in different connections:
https://github.com/dbeaver/dbeaver/issues/3605#issuecomment-590405154
Related
My ssis package has an oledb source which joins oracle and sql server to get source data and loads it into sql server oledb destination. Earlier we were using linked server for this purpose but we cannot use linked server anymore.
So I am taking the data from sql server and want to return it to the in clause of the oracle query which i am keeping as sql command oledb source.
I tried parsing an object type variable from sql server and putting it into the in clause of oracle query in oledb source but i get error that oracle cannot have more than 1000 literals in the in statement. So basically I think I have to do something like this:
select * from oracle.db where id in (select id from sqlserver.db).
Since I cannot use linked server so i was thinking if I could have a temp table which can be used throughout the package.
I tried out another way of using merge join in ssis. but my source data set is really large and the merge join is returning fewer rows than expecetd. I am badly stuck at this point. I have tried a number if things nothung seems to be working.
Can someone please help. Any help will be greatly appreciated.
A couple of options to try.
Lookup:
My first instinct was a Lookup Task, but that might not be a great solution depending on the size of your data sets, since all of the records from both tables have to pulled over the wire and stored in memory on the SSIS server. But if you were able to pull off a Merge Join, then a Lookup should also work, but it might be slow.
Set an OLE DB Source to pull the Oracle data, without the WHERE clause.
Set a Lookup to pull the id column from your SQL Server table.
On the General tab of the Lookup, under Specify how to handle rows with no matching entries, select Redirect rows to no-match output.
The output of the Lookup will just be the Oracle rows that found a matching row in your SQL Server query.
Working Table on the Oracle server
If you have the option of creating a table in the Oracle database, you could create a Data Flow Task to pipe the results of your SQL Server query into a working table on the Oracle box. Then, in a subsequent Data Flow, just construct your Oracle query to use that working table as a filter.
Probably follow that up with an Execute SQL Task to truncate that working table.
Although this requires write access to Oracle, it has the advantage of off-loading the heavy lifting of the query to the database machine, and only pulling the rows you care about over the wire.
I'd like to preface this by saying I'm not a DBA, so sorry for any gaps in technical knowledge.
I am working within a microservices architecture, where we have about a dozen or applications, each supported by its Postgres database instance (which is in RDS, if that helps). Each of the microservices' databases contains a few tables. It's safe to assume that there's no naming conflicts across any of the schemas/tables, and that there's no sharding of any data across the databases.
One of the issues we keep running into is wanting to analyze/join data across the databases. Right now, we're relying on a 3rd Party tool that caches our data and makes it possible to query across multiple database sources (via the shared cache).
Is it possible to create read-replicas of the schemas/tables from all of our production databases and have them available to query in a single database?
Are there any other ways to configure Postgres or RDS to make joining across our databases possible?
Is it possible to create read-replicas of the schemas/tables from all of our production databases and have them available to query in a single database?
Yes, that's possible and it's actually quite easy.
Setup one Postgres server that acts as the master.
For each remote server, create a foreign server then you then use to create a foreign table that makes the data accessible from the master server.
If you have multiple tables in multiple server that should be viewed as a single table in the master, you can setup inheritance to make all those tables appear like one. If you can define a "sharding" key that identifies a distinct attribute between those server, you can even make Postgres request the data only from the specific server.
All foreign tables can be joined as if they were local tables. Depending on the kind of query, some (or a lot) of the filter and join criteria can even be pushed down to the remote server to distribute the work.
As the Postgres Foreign Data Wrapper is writeable, you can even update the remote tables from the master server.
If the remote access and joins is too slow, you can create materialized views based on the remote tables to create a local copy of the data. This however means that it's not a real time copy and you have to manage the regular refresh of the tables.
Other (more complicated) options are the BDR project or pglogical. It seems that logical replication will be built into the next Postgres version (to be released a the end of this year).
Or you could use a distributed, shared-nothing system like Postgres-XL (which probably is the most complicated system to setup and maintain)
i have two database cvtl and cvtl_db , i need to write a single query to retrieve data from table A in cvtl and table B in cvtl_db.
Postgres is throwing error: cross database reference are not implemented
Basically you have two ways:
Older tools.
If you need to support older versions of PostgreSQL, use dblink or DBI-link. These two provide robust support for cross-db queries across a number of PostgreSQL versions. pl/proxy is another possibility.
Newer tools.
The newer approach is to use foreign data wrappers. This has more functionality (such as better transaction handling) and probably has more eyes in terms of support than dblink etc do today.
I am new to the PostgreSQL database. What my visual c++ application needs to do is to create multiple tables and add/retrieve data from them.
Each session of my application should create a new and distinct database. I can use the current date and time for a unique database name.
There should also be an option to delete all the databases.
I have worked out how to connect to a database, create tables, and add data to tables. I am not sure how to make a new database for each run or how to retrieve number and name of databases if user want to clear all databases.
Please help.
See the libpq examples in the documentation. The example program shows you how to list databases, and in general how to execute commands against the database. The example code there is trivial to adapt to creating and dropping databases.
Creating a database is a simple CREATE DATABASE SQL statement, same as any other libpq operation. You must connect to a temporary database (usually template1) to issue the CREATE DATABASE, then disconnect and make a new connection to the database you just created.
Rather than creating new databases, consider creating new schema instead. Much less hassle, since all you need to do is change the search_path or prefix your table references, you don't have to disconnect and reconnect to change schemas. See the documentation on schemas.
I question the wisdom of your design, though. It is rarely a good idea for applications to be creating and dropping databases (or tables, except temporary tables) as a normal part of their operation. Maybe if you elaborated on why you want to do this, we can come up with solutions that may be easier and/or perform better than your current approach.
I am working on a project where I need to programmatically validate and/or compare a database schema between product releases.
I am using Perl and am looking for a cross-platform method to collect the database schema. I am currently able to perform database queries by utilizing the dbisql.exe command and then parsing the results.
I am wondering if there is potentially a stored procedure or set of queries that I can run to collect the database schema.
It appears that the dbunload.exe command could be used to generate a SQL regeneration script however I am thinking that this output may be difficult to parse.
Any feedback would be greatly appreciated.
If you would like to retrieve the DB schema data on a really low level you could query the corresponding system tables. They are in the SYS-Namespace, especially SYSTABLE (for all tables) and SYSCOLUMN for all fields in those tables.
Check the ASA SQL Reference Handbook for the schema of those system tables.
With Perl's DBI you can easily fire queries on those tables. But you will have to create some local storage for the schema to compare the query results with.
Sybase Central v3.0 has the possibility to export DDL with all DB objects;
and I think SC v6.0 can't connect to ASA 11 :(