I have a situation where I need to update tables in different schemas in a single transaction.I can either use a plain JDBC or a Spring JDBCtemplate.
Any suggestions as to how I can achieve this.Thanks.
Ravi
I suggest you make your database connection from java with a specific user (say JAVA_USR or something like that), and ask your DBA for the proper grants over the destination schemas. Your DBA will like too to know that all the accesses from java applications are made from the same user, since it will make monitoring easier for them.
This way you can send the following alter statements through JDBC or SpringTemplate:
ALTER TABLE JOE.TABLE_1 ADD NAME VARCHAR2(80)
ALTER TABLE MARVIN.TABLE_2 ADD SURNAME VARCHAR2(100)
ALTER TABLE JACK.TABLE_3 ADD ADDRESS VARCHAR2(75)
...
If all the schemas are in the same database, you should be able to do your job in the same transaction in either of the ways you have asked about.
Related
I am creating a simple application where I am using a Servlet and JDBC to create users.
Is there any way I can use a trigger to insert the username into another table when the Oracle user is created with:
create user xyz ......
Once this query executes successfully, it inserts the user information in the DBA_USERS table.
I want the username to also be inserted into another table. Should I add it to that other table manually through JDBC, or can I create a trigger to do it automatically?
You could use a system trigger based on the create user DDL (but not a DML trigger on the dba_users view - you can't do that anyway, but don't even think about trying to do anything based on the data dictionary). But you wouldn't really have any way for that to know if the user being created is actually an application user - you'd be assuming any user added to the DB could only be related to your application.
Since you have to take other steps anyway - such as granting roles and/or privileges, maybe adding other application security data, etc., it probably makes more sense to do the table insert manually.
It may even make more sense to put all the user-creation code into a stored (and probably packaged) procedure, and just call that over JDBC; the downside of that is that the create user and any other DDL would need to be executed from within the procedure as dynamic SQL. Any of your own table inserts would be together though, and you'd only have that single JDBC call to make.
You can also have other procedures to modify and delete users.
Something to bear in mind, however you do it, is that DDL implicitly commits. Not necessarily a problem, just something to be aware of, so you can order the steps in a recoverable way.
I installed Oracle on my system, so now orcl is the SID, which is the unique identifier of my database instance.
Now starter db was created as part of the installation. I created 2 users user1 and user2 using the system account.
Using SQL developer I am accessing the users, this shows me 2 different connections with all the database objects like tables, stored procedures views etc.
so
When using these 2 users, am I accessing the same database? I am giving all the ddl commands by logging into the user1 or user 2, does all this data goes into the same .dbf file?
The database instance can be connected to only one database, then does this essentially mean that everytime I create a new database, to make a database instance to point to that, I need to do a configuration change?
In my experience with Oracle, the typical unit of division is a schema. Schemas in Oracle are used more like you would use databases in SQL Server or PostgreSQL. They represent both users and a logical separation of objects. Physical separation would usually be done using tablespaces. Tablespaces are a group of physical files where data is stored. Schemas can share or use different tablespaces. Having one tablespace per schema is uncommon; they usually share a few tablespaces or often even just one.
With that in mind, to answer your questions more directly,
1) Like in any other database, you can specify the schema the object belongs to:
CREATE TABLE MY_SCHEMA.TABLE_X ( X NUMBER )
If the schemas on two CREATE statements are different, then it will create different objects. What's different in Oracle is that the default schema changes for every user. The default schema is always the currently connected schema/user. So if you omit the schema like so:
CREATE TABLE TABLE_X ( X NUMBER )
then the implied schema is the currently connected schema/user. So if I'm logged in as MY_SCHEMA, then the above is equivalent to the first example. When connecting as two different users, then the implied schema will be different and the DDL is not equivalent between the two users. So running the same statement would create two different objects if you do not specify a schema.
The two objects may be stored in the same physical file if they are in the same tablespace. (They are most likely in the USERS tablespace if you did not create one explicitly and did not specify a different default tablespace when creating the schemas.) Regardless, they are still two completely separate objects.
If you specify the schema explicitly like in the first example, then the DDL is equivalent regardless of who executes it (although permissions may prevent some users from executing it). So it would result in creating the object once, and attempting to create it a second time would result in an error unless you're using CREATE OR REPLACE or something similar.
2) I don't know the answer to this question, but as I said, in Oracle, the basic unit of separation is usually the schema, not a database. I believe the question you're asking is a large part of the reason why the schemas are used in the way they are. Having multiple actual databases on the same machine/instance is far more difficult in Oracle than in other databases (if not impossible), so it's much simpler to have a single database with many schemas.
I've database with 15 tables. Now due to development process one column has to added to all the tables in the database. This changes should not affect the existing process because some other services are also consuming this database. So to accomplish it I thought of creating a new database. Is there are any other way to do it.
Usually it should be enough to create a new schema ("user") and create the tables in that new schema. In Oracle, identically named tables can exist in several schemas.
CREATE USER xxx IDENTIFIED BY yyy
you can create another schema for development and import the table to new schema.Developer should use the development schema instead of production schema.you can also create new database and import from current database but it might be last option
What's wrong with alter table T add (COL varchar2(5)); ?
Of course dependend stored procedures or packages become invalid.
You can leave them alone, then the first call would return an exception and auto-recompile the called procedure. Or you can alter procedure P compile;.
I have a schema called "CUSTOMERS". In this schema there is a table called RECEIVABLES.
There is another schema called "ACCOUNTS". In this schema, there is a table called RECEIVABLES_AC.
RECEIVABLES_AC has a public synoym called RECEIVABLES.
The table structure of both the tables is exactly the same.
If your front-end uses the customer schema credentials to establish a connection, how can you ensure that the record will get inserted in RECEIVABLES_AC without changing the front-end code.
I think this is a trick question. Short of renaming the table RECEIVABLES in the CUSTOMERS schema, I don't see how this can be done.
The only way that I can think of (without changing the login or insert statement) is to use a database trigger that runs on login and changes the current schema to ACCOUNTS:
create or replace trigger logon_set_schema
AFTER LOGON ON DATABASE
BEGIN
if sys_context('USERENV','SESSION_USER') = 'CUSTOMERS' then
execute immediate 'alter session set current_schema=accounts';
end if
END;
/
However, this would likely break other aspects of the code, so changing the application to specify the schema name would be vastly preferable.
What isn't specified is if the behavior is supposed to be instead-of or in-addition-to.
Use replication on ACCOUNTS.RECEIVABLES to propagate DML to CUSTOMER.RECEIVABLES_AC. Triggers, streams, what have you.
Use the ALTER SESSION SET CURRENT_SCHEMA statement to change the default namespace of the user's session.
The right way to respond is to fix the design, and to not have multiple receivables tables with public schemas floating about.
Two good ways to solve this problem are:
Option 1
Rename CUSTOMERS.RECEIVABLES.
Drop the public synonym.
Create a private synonym in the CUSTOMERS schema, called RECEIVABLES that points to ACCOUNTS.RECEIVABLES_AC.
Option 2
Change the front-end to refer to RECEIVABLES_AC instead of RECEIVABLES.
Create a private synonym in the CUSTOMERS schema, called RECEIVABLES_AC that points to ACCOUNTS.RECEIVABLES_AC.
I would prefer Option 2. Private synonyms are a great way of controlling which tables are used by a particular schema, without having to hard-code the schema name in the app.
The database user has got two schemas. I need to read the data from a specific schema using ado.net. I am using OleDbConnection object to create the connection to database. Appreciate your answers.
Use SCHEMA_NAME.TABLE_NAME in your queries.
If you don't specify a schema, Oracle will look into the current schema. The schema is by default the connexion user (so if you connect with USER1 and query TABLE1, Oracle will look for the table USER1.TABLE1). You can change your current schema at any time during a session with:
ALTER SESSION SET CURRENT_SCHEMA=SCHEMA2;
You can also use synonyms to point to the correct table.