In Oracle, is it possible to store in one tablespace the data for two tables that share the same name but are defined for different users (schemas)?
Or maybe I need to create separate tablespace per user if there might be a name clash?
I cannot easily check it for myself, as I dont' have any instance with proper privilliges available currently.
If you mean you have 2 users (schemas) so yes you can create 2 tables with same name with different users for example create table user1.tab1 ... and create table user2.tab1 ...
I need to create separate tablespace per user if there might be a name
clash
let me do some explanation ..in oracle you already have several users , for example system users that as it obvious have high privileges then you have/create other users that have specific privilege , every users has his own objects, his own tables , procedure... and this users and its objects normally and can resides in one datafiles which the datafile resides in the tablespace.
Can you grant privilege to allows the creation of a global temporary table ONLY, i.e. without CREATE TABLE?
The background of this stems from security models that don't allow 'CREATE TABLE'... I can't find a reference to any specific privileges.
I can't find a reference to any specific privileges.
Because, as far as I know, there is none. You'll still have to grant CREATE TABLE privilege to a user so he could create TEMPORARY tables.
In order to prevent a user from creating regular tables, and allow him to create only temporary tables you might consider the following:
Grant CREATE TABLE privilege to a user and revoke quota on a specific tablespace.
alter user <<user_name>> quota 0M on <<tablespace>>;
It might be the user's default tablespace or a different one.
In Oracle's versions with no DEFFERED_SEGMENT_CREATION it'll be enough for the user to see space quota exceeded for tablespace when he/she tries to create a regular table.
In Oracle's version with DEFFERED_SEGMENT_CREATION a user will still be able to create regular tables, but will not be able populate them. The second the user tries to execute an INSERT statement the space quota exceeded for tablespace appears.
So you might consider setting deferred_segment_creation parameter to false.
alter system set deferred_segment_creation = false;
I am new to PL/SQL Developer, and I used the File->New->Table option to create a new table. After using the GUI to set up my table descriptions, when I click "apply" I get the error "no privileges on table space".
I tried googling a solution and I read that I need to give the owner of the schema privileges to modify this table. How do I determine who the owner of a schema is so that I can give them privileges?
Is there another solution to this issue that I do not know of?
You have created the table, so it belongs to you, there is no need to grant something on schema level.
A different story altogether is the tablespace in which the table is created. There, you need a quota. With a privileged user, you can give the quote like so:
alter user <your-username>
quota unlimited on <tablespace-name>;
You need someone with sysdba privileges on the database your schema belongs to (typically a DBA) to grant your schema the necessary privileges to create objects (tables, procedures etc), along with a quota on the tablespace in question.
A third party product we have at my company uses Oracle as a backend. I'm attempting to log into the Oracle database and look at the schema and data. I've logged in as sys/sysdba, created a user with a default tablespace of that created by the application, and granted the user all necessary permissions to query the structures. I've also set O7_DICTIONARY_ACCESSIBILITY to true to allow querying of the data dictionary objects.
After logging in as the user and querying User_Tables nothing is returned. But when I query DBA_Tables the tables I'd expect to find are returned. I'm new to Oracle so I'm not quite certain how a non-system table can be in the tablespace, but not a user_table.
More importantly, how do you query the data in these tables? Whenever I attempt a simple "Select *" from the tables I get a "table or view does not exist" error.
Thanks in advance.
The default tablespace you set for a user controls what tablespace objects owned by that user are created in. It has nothing to do with what objects they can query.
USER_TABLES returns information about the tables that a particular user owns. It does not sound like your user owns any tables, so you would expect that to be empty.
ALL_TABLES returns information about the tables that a particular user has access to. If you granted the appropriate privileges, your user should see the tables in this data dictionary view.
DBA_TABLES returns information about every table in the database even if you don't necessarily have access to the underlying table.
If you are trying to query data from one of the tables, are you specifying the schema name (the OWNER column in ALL_TABLES)? If you do not own an object, you generally need to use fully qualified names to reference it, i.e.
SELECT *
FROM schema_owner.table_name
You can avoid using fully qualified names if
You create a synonym (public or private) for the object
You change the CURRENT_SCHEMA for the session. This changes the default schema that a name is resolved under. It does not affect permissions and privileges. You can change the current schema with the command
ALTER SESSION SET current_schema = new_schema_name
You would have to do this for each session the user creates-- potentially in a login trigger.
What is the difference between a user and a schema in Oracle?
From Ask Tom
You should consider a schema to be the user account and collection of all objects therein
as a schema for all intents and purposes.
SCOTT is a schema that includes the EMP, DEPT and BONUS tables with various grants, and
other stuff.
SYS is a schema that includes tons of tables, views, grants, etc etc etc.
SYSTEM is a schema.....
Technically -- A schema is the set of metadata (data dictionary) used by the database,
typically generated using DDL. A schema defines attributes of the database, such as
tables, columns, and properties. A database schema is a description of the data in a
database.
I believe the problem is that Oracle uses the term schema slightly differently from what it generally means.
Oracle's schema (as explained in Nebakanezer's answer): basically the set of all tables and other objects owned by a user account, so roughly equivalent to a user account
Schema in general: The set of all tables, sprocs etc. that make up the database for a given system / application (as in "Developers should discuss with the DBAs about the schema for our new application.")
Schema in sense 2. is similar, but not the same as schema in sense 1. E.g. for an application that uses several DB accounts, a schema in sense 2 might consist of several Oracle schemas :-).
Plus schema can also mean a bunch of other, fairly unrelated things in other contexts (e.g. in mathematics).
Oracle should just have used a term like "userarea" or "accountobjects", instead of overloadin "schema"...
From WikiAnswers:
A schema is collection of database objects, including logical structures such as tables, views, sequences, stored procedures, synonyms, indexes, clusters, and database links.
A user owns a schema.
A user and a schema have the same name.
The CREATE USER command creates a user. It also automatically creates a schema for that user.
The CREATE SCHEMA command does not create a "schema" as it implies, it just allows you to create multiple tables and views and perform multiple grants in your own schema in a single transaction.
For all intents and purposes you can consider a user to be a schema and a schema to be a user.
Furthermore, a user can access objects in schemas other than their own, if they have permission to do so.
Think of a user as you normally do (username/password with access to log in and access some objects in the system) and a schema as the database version of a user's home directory. User "foo" generally creates things under schema "foo" for example, if user "foo" creates or refers to table "bar" then Oracle will assume that the user means "foo.bar".
This answer does not define the difference between an owner and schema but I think it adds to the discussion.
In my little world of thinking:
I have struggled with the idea that I create N number of users where I want each of these users to "consume" (aka, use) a single schema.
Tim at oracle-base.com shows how to do this (have N number of users and each of these users will be "redirected" to a single schema.
He has a second "synonym" approach (not listed here). I am only quoting the CURRENT_SCHEMA version (one of his approaches) here:
CURRENT_SCHEMA Approach
This method uses the CURRENT_SCHEMA session attribute to automatically
point application users to the correct schema.
First, we create the schema owner and an application user.
CONN sys/password AS SYSDBA
-- Remove existing users and roles with the same names.
DROP USER schema_owner CASCADE;
DROP USER app_user CASCADE;
DROP ROLE schema_rw_role;
DROP ROLE schema_ro_role;
-- Schema owner.
CREATE USER schema_owner IDENTIFIED BY password
DEFAULT TABLESPACE users
TEMPORARY TABLESPACE temp
QUOTA UNLIMITED ON users;
GRANT CONNECT, CREATE TABLE TO schema_owner;
-- Application user.
CREATE USER app_user IDENTIFIED BY password
DEFAULT TABLESPACE users
TEMPORARY TABLESPACE temp;
GRANT CONNECT TO app_user;
Notice that the application user can connect, but does not have any
tablespace quotas or privileges to create objects.
Next, we create some roles to allow read-write and read-only access.
CREATE ROLE schema_rw_role;
CREATE ROLE schema_ro_role;
We want to give our application user read-write access to the schema
objects, so we grant the relevant role.
GRANT schema_rw_role TO app_user;
We need to make sure the application user has its default schema
pointing to the schema owner, so we create an AFTER LOGON trigger to
do this for us.
CREATE OR REPLACE TRIGGER app_user.after_logon_trg
AFTER LOGON ON app_user.SCHEMA
BEGIN
DBMS_APPLICATION_INFO.set_module(USER, 'Initialized');
EXECUTE IMMEDIATE 'ALTER SESSION SET current_schema=SCHEMA_OWNER';
END;
/
Now we are ready to create an object in the schema owner.
CONN schema_owner/password
CREATE TABLE test_tab (
id NUMBER,
description VARCHAR2(50),
CONSTRAINT test_tab_pk PRIMARY KEY (id)
);
GRANT SELECT ON test_tab TO schema_ro_role;
GRANT SELECT, INSERT, UPDATE, DELETE ON test_tab TO schema_rw_role;
Notice how the privileges are granted to the relevant roles. Without
this, the objects would not be visible to the application user. We now
have a functioning schema owner and application user.
SQL> CONN app_user/password
Connected.
SQL> DESC test_tab
Name Null? Type
----------------------------------------------------- -------- ------------------------------------
ID NOT NULL NUMBER
DESCRIPTION VARCHAR2(50)
SQL>
This method is ideal where the application user is simply an
alternative entry point to the main schema, requiring no objects of
its own.
It's very simple.
If USER has OBJECTS
then call it SCHEMA
else
call it USER
end if;
A user may be given access to schema objects owned by different Users.
Schema is an encapsulation of DB.objects about an idea/domain of intrest, and owned by ONE user. It then will be shared by other users/applications with suppressed roles. So users need not own a schema, but a schema needs to have an owner.
--USER and SCHEMA
The both words user and schema are interchangeble,thats why most people get confusion on this words below i explained the difference between them
--User User is a account to connect database(Server). we can create user by using CREATE USER user_name IDENTIFIED BY password .
--Schema
Actually Oracle Database contain logical and physical strucutre to process the data.The Schema Also Logical Structure to process the data in Database(Memory Component). Its Created automatically by oracle when user created.It Contains All Objects created by the user associated to that schema.For Example if i created a user with name santhosh then oracle createts a schema called santhosh,oracle stores all objects created by user santhosh in santhosh schema.
We can create schema by CREATE SCHEMA statement ,but Oracle Automatically create a user for that schema.
We can Drop the schema by using DROP SCHEMA schama_name RESTRICT statement but it can not delete scehema contains objects,so to drop schema it must be empty.here the restrict word forcely specify that schema with out objects.
If we try to drop a user contain objects in his schema we must specify CASCADE word because oracle does not allow you to delete user contain objects.
DROP USER user_name CASCADE
so oracle deletes the objects in schema and then it drops the user automatically,Objects refered to this schema objects from other schema like views and private synonyms goes to invalid state.
I hope now you got the difference between them,if you have any doubts on this topic,please feel free to ask.
Thank you.
A user account is like relatives who holds a key to your home, but does not own anything i.e. a user account does not own any database object...no data dictionary...
Whereas a schema is an encapsulation of database objects. It's like the owner of the house who owns everything in your house and a user account will be able to access the goods at the home only when the owner i.e. schema gives needed grants to it.
A schema and database users are same but if schema has owned database objects and they can do anything their object but user just access the objects, They can't DO any DDL operations until schema user give you the proper privileges.
Based on my little knowledge of Oracle... a USER and a SCHEMA are somewhat similar. But there is also a major difference. A USER can be called a SCHEMA if the "USER" owns any object, otherwise ... it will only remain a "USER". Once the USER owns at least one object then by virtue of all of your definitions above.... the USER can now be called a SCHEMA.
User: Access to resource of the database. Like a key to enter a house.
Schema: Collection of information about database objects. Like Index in your book which contains the short information about the chapter.
Look here for details
For most of the people who are more familiar with MariaDB or MySQL this seems little confusing because in MariaDB or MySQL they have different schemas (which includes different tables, view , PLSQL blocks and DB objects etc) and USERS are the accounts which can access those schema. Therefore no specific user can belong to any particular schema. The permission has be to given to that Schema then the user can access it. The Users and Schema is separated in databases like MySQL and MariaDB.
In Oracle schema and users are almost treated as same. To work with that schema you need to have the permission which is where you will feel that the schema name is nothing but user name. Permissions can be given across schemas to access different database objects from different schema. In oracle we can say that a user owns a schema because when you create a user you create DB objects for it and vice a versa.
Schema is a container of objects.
It is owned by a user.
Well, I read somewhere that if your database user has the DDL privileges then it's a schema, else it's a user.