I created two H2 databases and I am unable to link the database. I have achieved to link the databases in ORACLE through CREATE DATABASE LINK. We have similar DB Link in POSTGRES DB also. Do we have any way to link the DATABASE in H2 ?
You cannot link the whole database, but you can link individual tables with CREATE LINKED TABLE command:
https://h2database.com/html/commands.html#create_linked_table
There is a helper LINK_SCHEMA function to create table links for all tables in the specified schema:
https://h2database.com/html/functions.html#link_schema
Related
I hope someone can help me to learn about Postgres schema and databases.
I have Postgres database called db1 and it has table calls table1.
all these objects are in default schema called public.
Then I created another database called db2 and created another table with same name table1.
I didn't got any error but both tables are in same schema called public.
I created indexes for both of these tables and they both refer the table as public.table1.
I wonder a setup like this will give issue or not? If yes, then should I create different schemas for each database if I'm going to use same table names in all databases?
In Postgres a database is the highest level "container". Then schemas follow. There can be schemas with the same name in different databases (but no in the same database). The other databases won't "see" them. So there is no problem in your setup.
Can we have two Postgres databases in same schema?
The answer is no. The relevant PostgreSQL documentation shows the hierarchy:
database.schema.table
This diagram (taken from this answer) is useful to visualise the relationship:
I have two companies using same application running in Oracle Database. Now the companies are merging and making a single company. The databases are huge with an approximate size of 10 TB.
We wanted to have the application in two databases to be merged and have a single application pointed to both the databases with minimal work.
Help is highly appreciated.
Regards
Bjm
Using DB Links feature in Oracle
For more information you can use below link regarding Database Links:
https://docs.oracle.com/cd/B28359_01/server.111/b28310/ds_concepts002.htm#ADMIN12083
It would enable you to build a SQL statement that references tables from the two different databases.
If you want to access the data in instance B from the instance A, you can use below query and edit the details accordingly:
CREATE DATABASE LINK dblink_example
CONNECT TO xxusernamexx IDENTIFIED BY xxpasswordxx
USING
'(DESCRIPTION=
(ADDRESS=
(PROTOCOL=TCP)
(HOST=xxipaddrxx / xxhostxx )
(PORT=xxportxx))
(CONNECT_DATA=
(SID=xxsidxx)))';
Now you can execute the below query to access the table:
SELECT * FROM tablename#dblink_example;
You can perform any operation DML, DDL, DQL using DB Link
I am trying to see the tables I've made in my project with h2 in the sql workbench, but after connecting to my database I only see this snapshot:
how can I see and access the contents of my database?
Tables can be show by using show tables
You can write queries by going to view > statement.
We are using H2 as test database for junittest suite. The actual application has tables in multiple databases like db1.s1.table1 and db2.s1.table2 (in other words database.schema.tablename) . To replicate that functionality we need to create two databases db1 and db2 and then create schema and tables accordingly. Also we have a dbscript.sql which loads all data before running test suite.
Please let us know if there is a way to create multiple databases in H2. If yes, what will be the exact command to do that as part of the script.
Since H2 creates the database specified as part of jdbc URL. Is there a way to specify multiple databases as part of URL so we can have them created.
I want to load data from one database table to another database table.
For example there exists table 'tbl' in db1 and db2 databases, and I want to copy all data from 'tbl' of 'db1' to 'tbl' of 'db2' in oracle.
Any help would be appreciated.
I would make use of either exp/imp or expdp/impdp (10g+) for this.
The older exp/imp command is slower, but has the advantage that the export file is created and read from the client system. The expdp/impdp command is much faster, but the file is created on and read from the server where the databases live. So, if you have your databases on different servers, you'll need to copy the export files around. Also, it requires an Oracle Directory to be set up by the DBA.
In order to do this , you will need to create a database link between the two schemas. Here is a link to a tutorial that may help.