Create table and call it from sql - sql

Question

I have a PL/SQL function which creates a new temporary table. For creating the table I use execute immediate. When I run my function in oracle sql developer everything is ok; the function creates the temp table without errors. But when U use SQL:
Select function_name from table_name
I get an exceptions:
ORA-14552: cannot perform a DDL, commit or rollback inside a query or DML
ORA-06512: at "SYSTEM.GET_USERS", line 10
14552. 00000 - "cannot perform a DDL, commit or rollback inside a query or DML "
*Cause: DDL operations like creation tables, views etc. and transaction
control statements such as commit/rollback cannot be performed
inside a query or a DML statement.
Update
Sorry, write from tablet PC and have problems with format text. My function:
CREATE OR REPLACE FUNCTION GET_USERS
(
USERID IN VARCHAR2
)
RETURN VARCHAR2
AS
request VARCHAR2(520) := 'CREATE GLOBAL TEMPORARY TABLE ';
BEGIN
request := request || 'temp_table_' || userid ||
'(user_name varchar2(50), user_id varchar2(20), is_administrator varchar2(5)') ||
' ON COMMIT PRESERVE ROWS';
EXECUTE IMMEDIATE (request);
RETURN 'true';
END GET_USERS;

Answer 1

The error is explicit:
ORA-14552: cannot perform a DDL, commit or rollback inside a query or DML
In Oracle, you can't commit inside a query. A likely explanation is that it would make no sense since a query in Oracle is atomic (either succeeds entirely or makes no change) and this couldn't work if you commit in the middle of a DML. For a select query, all rows must be returned from a single logical point-in-time and if you commit in the middle of a select you would have inconsistent results.
Since DDL in Oracle issue an implicit commit, you can't make DDL inside a query.
This should not be a problem in your case though: SQL server-like temporary tables are not equivalent to the GLOBALLY temporary table in Oracle. There is a reason why temp tables in Oracle are always prefixed with GLOBALLY: they are visible to all sessions although the data in the temporary table is private to each session.
In Oracle creating a temporary table is a relatively expensive operation and you should not create individual temporary tables: all sessions should that do the same job should use the same common structure. Instead of creating multiple temporary tables, in Oracle you should create the table once and reuse it in all procedures. If you are going to need it later, why drop it?
In any case, if you decide to do multiple DDL that depend upon a SELECT, you could do it in a PLSQL block instead of a SELECT query:
DECLARE
l VARCHAR2(100);
BEGIN
FOR cc IN (SELECT col FROM tab) LOOP
l := create_temp_table(cc.col);
END LOOP;
END;

Answer 2

I tested below solution on Oracle 10g XE, it works for me.
Create function:
CREATE OR REPLACE FUNCTION GET_USERS
(
USERID IN VARCHAR2
)
RETURN VARCHAR2
AS
request VARCHAR2(255) := 'CREATE GLOBAL TEMPORARY TABLE ';
BEGIN
request := request || 'temp_table_' || userid ||
'(user_name varchar2(50), user_id varchar2(20), is_administrator varchar2(5))' ||
' ON COMMIT PRESERVE ROWS';
EXECUTE IMMEDIATE request;
RETURN 'true';
END GET_USERS;
Run function:
SET SERVEROUTPUT ON
DECLARE
RESULT VARCHAR(255);
BEGIN
RESULT:=gET_USERS('ADMIN3');
dbms_output.put_line(result);
END;
and select from temporary table:
SELECT * FROM temp_table_admin3;