We have an existing database link in an Oracle database that links to data in a Sql Server database. Now, a 2nd Oracle database needs to use that same data. Due to security setup, the 2nd Oracle database cannot "see" the Sql Server database, but it can see the 1st Oracle database.
If we create a database link in the 2nd Oracle database that points to the 1st Oracle database, will we be able to query data from the Sql Server database in the 2nd Oracle database by going through 2 database links? Would the query syntax look like this:
SELECT * FROM myTable#2ndLink#1stLink
Has anyone done something like this before?
Vincent's solution will work, and another solution is to create a synonym instead of a view.
DB1:
CREATE SYNONYM X FOR MyTable#sqlServerDB
DB2:
(assumes db link to DB1 connects as owner of synonym)
SELECT * from X#DB1
I'm not sure this synthax would work (although it would be interesting to test it I can not do it right now). However, even if it doesn't work, you can still create a view in Database 1 that points to a table in your SQL Server Database. From Database 2, you could then query:
SELECT * FROM myView#db1
That would point to the correct table.
Related
I have two DBCS instance. DB1 and DB2. I want to access data of DB2 instance in DB1.
I dont want to copy the data , I just want to access for reporting purpose.
Can you please help me on the same.
Within DB1, create a db link to DB2:
CREATE PUBLIC DATABASE LINK "DB2"
CONNECT TO "db2user" IDENTIFIED BY "db2userpwd"
USING 'DB2';
Create a tnsnames.ora entry (in the tnsnames.ora of the DB1 machine) for DB2
Then when you want to select the data,
select * from my_db2_table#DB2;
Read more on DB Links in the SQL Reference.create database link
BTW, in the CREATE statement above, the two strings 'DB2' do not have to be the same, but probably should be for consistency. The first (CREATE DATABASE LINK DB2) is the name of the link and is what is referenced in the sample SELECT statement. The second (using 'DB2') is the reference to the tnsnames.ora entry.
Is there a way to replicate data(like triggers or jobs) from oracle tables to postgres tables and vice versa(for different set of tables) without using external tools? Just one way replication for both the scenarios.
Just a hint:
You can think of create a DB link from Oracle to Postgres which is called heterogeneous connectivity which makes it possible to select data from Postgres with a select statement in Oracle.
Then use materialized views to schedule and store the results of those selects.
As you don't want to use any external tool otherwise the solution should have been much simpler
for 20 tables I need to replicate data from oracle to postgres. For 40 different tables, I need to replicate from postgres to oracle.
I could imagine the following setup:
For the Oracles tables that need to be accessible from Postgres, simply create foreign tables inside the Postgres server. They appear to be "local" tables in the Postgres server, but the FDW ("foreign data wrapper") will forward any request to the Oracle server. So no replication required. Whether or not this will be fast enough depends on how you access the tables. Some operations (WHERE clause, ORDER BY etc) can be pushed down to the Oracle server, some will be done by the Postgres server after all the rows have been fechted.
For the Postgres tables that need to be replicated to Oracle you could have a similar setup: create a foreign table that points to the target table in Oracle. Then create triggers on the Postgres table that will update the foreign table, thus sending the changes to Oracle.
This could all be managed on the Postgres side.
I have the following scenario and need to solve it in ORACLE:
Table A is on a DB-server
Table B is on a different server
Table A will be populated with data.
Whenever something is inserted to Table A, i want to copy it to Table B.
Table B nearly has similar columns, but sometimes I just want to get
the content from 2 columns from tableA and concatenate it and save it to
Table B.
I am not very familiar with ORACLE, but after researching on GOOGLE
some say that you can do it with TRIGGERS or VIEWS, how would you do it?
So in general, there is a table which will be populated and its content
should be copien to a different table.
This is the solution I came up so far
create public database link
other_db
connect to
user
identified by
pw
using 'tns-entry';
CREATE TRIGGER modify_remote_my_table
AFTER INSERT ON my_table
BEGIN INSERT INTO ....?
END;
/
How can I select the latest row that was inserted?
If the databases of these two tables are in two different servers, then you will need a database link (db-link) to be created in Table A schema so that it can access(read/write) the Table B data using db-link.
Step 1: Create a database link in Table A server db pointing to Table B server DB
Step 2: Create a trigger for Table A, which helps in inserting data to the table B using database link. You can customize ( concatenate the values) inside the trigger before inserting it into table B.
This link should help you
http://searchoracle.techtarget.com/tip/How-to-create-a-database-link-in-Oracle
Yes you can do this with triggers. But there may be a few disadvantages.
What if database B is not available? -> Exception handling in you trigger.
What if database B was not available for 2h? You inserted data into database A which is now missing in database B. -> Do crazy things with temporarily inserting it into a cache table in database A.
Performance. Well, the performance for inserting a lot of data will be ugly. Each time you insert data, Oracle will start the PL/SQL engine to insert the data into the remote database.
Maybe you could think about using MViews (Materialized Views) to replicate the data via database link. Later you can build your queries so that they access tables from database B and add the required data from database A by joining the MViews.
You can also use fast refresh to replicate the data (almost) realtime.
From perspective of an Oracle Database Admin this would make a lot more sense than the trigger approach.
try this code
database links are considered rather insecure and oracle own options are having licences associated these days, some of the other options are deprecated as well.
https://gist.github.com/anonymous/e3051239ba401e416565cdd912e0de8c
uses ora_rowscn to sync tables across two different oracle databases.
I have a SQLite database and I need to connect to an Oracle database so I can do some reports.
So my questions are:
Is it possible to create a dblink from SQLite to the Oracle database, so that I can use something like:
select *
from sqlitetable s
join oracletable#oracleserver o on o.column = s.column
where s.column = 'x'
Assuming this is indeed possible, do I need to have some setup/support from the oracle admin, or can I simply connect via my existing account?
It is, in theory, possible to write a virtual table that links to Oracle.
However, I don't know of any actual implementation.
I am reverse-engineering an application which administers an Oracle database.
Everything is new to me (application + database)
There is a statement there somewhere, which is:
SELECT * FROM XXX#YYY (XXX is a word, YYY another word)
If I go into my database with TOAD I can't find an 'XXX#YYY' table nor view. If I copy paste the statement in TOAD's editor, I get results as if the table exists.
I know that the '#' symbol is allowed for naming an Oracle object. Is it possible that it means something else here though?
How can I find the table (or view)? Is it possible to get information through a statement such as which schema does 'XXX#YYY' belong to or weather it is a table or a view, so that I can track it?
The database consists of many schemas. There is a default one. Is it possible that XXX#YYY may belong to another schema, rather than the default?
Please help me find the table.
Identifier behind # is database link. It is a way to access objects on some remote Oracle server. more info on http://docs.oracle.com/cd/E11882_01/server.112/e26088/statements_5005.htm#SQLRF01205
In Toad/Oracle XXX#YYY means object#database_link.
Look for the schema in your DB, there you will find the table.
Btw: I think its better to use SCHEMA.TABLENAME
If you have problems finding the SCHEMA, go to View->Toad Options, select Treeview at Browser style and then it should display all schemas.