How to find schema name in Oracle ? when you are connected in sql session using read only user

I am connected to a oracle database with a read only user and i used service name while Setting up connection in sql developer hence i dont know SID ( schema ).

How can i find out schema name which i am connected to ?

I am looking for this because i want to generate ER diagram and in that process at one step it asks to select schema. When i tried to select my user name , i dint get any tables as i guess all tables are mapped with schema user.

Edit: I got my answer partially by the below sql Frank provided in comment , it gave me owner name which is schema in my case. But I am not sure if it is generic solution applicable for all cases.

select owner, table_name from all_tables. 

Edit: I think above sql is correct solution in all cases because schema is owner of all db objects. So either i get schema or owner both are same. Earlier my understanding about schema was not correct and i gone through another question and found schema is also a user.

Frank/a_horse_with_no_name Put this in answer so that i can accept it.

3 Answers

Call SYS_CONTEXT to get the current schema. From Ask Tom "How to get current schema:

select sys_context( 'userenv', 'current_schema' ) from dual; 

To create a read-only user, you have to setup a different user than the one owning the tables you want to access.

If you just create the user and grant SELECT permission to the read-only user, you'll need to prepend the schema name to each table name. To avoid this, you have basically two options:

1. Set the current schema in your session:

ALTER SESSION SET CURRENT_SCHEMA=XYZ 

2. Create synonyms for all tables:

CREATE SYNONYM READER_USER.TABLE1 FOR XYZ.TABLE1 

So if you haven't been told the name of the owner schema, you basically have three options. The last one should always work:

1. Query the current schema setting:

SELECT SYS_CONTEXT('USERENV','CURRENT_SCHEMA') FROM DUAL 

2. List your synonyms:

SELECT * FROM ALL_SYNONYMS WHERE OWNER = USER 

3. Investigate all tables (with the exception of the some well-known standard schemas):

SELECT * FROM ALL_TABLES WHERE OWNER NOT IN ('SYS', 'SYSTEM', 'CTXSYS', 'MDSYS'); 

How about the following 3 statements?

-- change to your schema

ALTER SESSION SET CURRENT_SCHEMA=yourSchemaName; 

-- check current schema

SELECT SYS_CONTEXT('USERENV','CURRENT_SCHEMA') FROM DUAL; 

-- generate drop table statements

SELECT 'drop table ', table_name, 'cascade constraints;' FROM ALL_TABLES WHERE OWNER = 'yourSchemaName'; 

COPY the RESULT and PASTE and RUN.