Variable database name in SQL Server query using Oracle database link

Question

Hi All,
I have an ApEx 4.1 app running on 11g x64 (11.2.0.1) on Windows Server 2008 x64, and I have some data integration points with a SQL Server (2005 and 2008) that I need to establish. I have configured the database link with dg4odbc and it works beautifully... I can execute queries against the SQL Server database without any problems using the database link.
However, there is a scenario where the SQL Server database name is dynamic, and I need to generate it on the fly in a PL/SQL block, and then use that in a dynamic SQL query (all of this in ApEx). This is where I run into problems... when I am querying the default database based on the ODBC connection and I don't have to specify the database name, there is no issue. But when I need to access one of several other non-default databases, I keep receiving the "invalid table" error.
This runs fine:* (note that "fv" is the name of my database link)
v_query1 := 'select "ReleaseDate" from dbo.Schedules@fv where dbo.Schedules."SchedID" = :schedule';
EXECUTE IMMEDIATE v_query1 into rel_date using schedule;
I then take that rel_date variable, convert to a varchar2 (rel_date_char), and then use it as the database name in the next query...
This returns an error_ (Error ORA-00903: invalid table name)
v_query2 := 'select "PARTNO" from :rel_date_char.dbo.ProdDetails@fv where "SchedID" = :schedule and "UnitID" = :unit
and "MasterKey" = :master and "ParentKey" = :parent';
EXECUTE IMMEDIATE v_query2 into part_number using schedule, unit, master, parent;
I have also tried using all of the following to no avail:
'select "PARTNO" from ' || :rel_date_char || '.dbo.ProdDetails@fv where "SchedID"...
'select "PARTNO" from ' || rel_date_char || '.dbo.ProdDetails@fv where "SchedID"...
'select "PARTNO" from ' || @rel_date_char || '.dbo.ProdDetails@fv where "SchedID"...
'select "PARTNO" from @rel_date_char.dbo.ProdDetails@fv where "SchedID"...
Is there a way to do this in PL/SQL?
Thanks for any help!
-Ian C.
Edited by: 946532 on Jul 15, 2012 7:45 PM

Answer 1

Just did a test using passthrough:
SQL> set serveroutput on
SQL> declare
2 val varchar2(100);
3 c integer;
4 nr integer;
5 begin
6 c:= dbms_hs_passthrough.open_cursor@FREETDS_DG4ODBC_EMGTW_11_2_0_3;
7 dbms_hs_passthrough.parse@FREETDS_DG4ODBC_EMGTW_11_2_0_3 (c, 'select count(*) from EMP');
8 LOOP
9 nr:= DBMS_Hs_Passthrough.fetch_row@FREETDS_DG4ODBC_EMGTW_11_2_0_3(c);
10 exit when nr=0;
11 dbms_hs_passthrough.get_value@FREETDS_DG4ODBC_EMGTW_11_2_0_3(c,1,val);
12 dbms_output.put_line(val);
13 end loop;
14 dbms_hs_passthrough.close_cursor@FREETDS_DG4ODBC_EMGTW_11_2_0_3(c);
15 end;
16 /
24576
PL/SQL procedure successfully completed.
SQL> declare
2 val varchar2(100);
3 c integer;
4 nr integer;
5 begin
6 c:= dbms_hs_passthrough.open_cursor@FREETDS_DG4ODBC_EMGTW_11_2_0_3;
7 dbms_hs_passthrough.parse@FREETDS_DG4ODBC_EMGTW_11_2_0_3 (c, 'select count(*) from dbo.EMP');
8 LOOP
9 nr:= DBMS_Hs_Passthrough.fetch_row@FREETDS_DG4ODBC_EMGTW_11_2_0_3(c);
10 exit when nr=0;
11 dbms_hs_passthrough.get_value@FREETDS_DG4ODBC_EMGTW_11_2_0_3(c,1,val);
12 dbms_output.put_line(val);
13 end loop;
14 dbms_hs_passthrough.close_cursor@FREETDS_DG4ODBC_EMGTW_11_2_0_3(c);
15 end;
16 /
24576
PL/SQL procedure successfully completed.
So all 3 ways work for me.
Edited by: kgronau on Jul 23, 2012 10:08 AM
Now using variables to perform the select:
SQL> declare
2 val varchar2(100);
3 c integer;
4 nr integer;
5 tabname varchar2(20) :='EMP';
6 ownr varchar2(20) :='dbo';
7 dbname varchar2(20) :='gateway';
8 begin
9 c:= dbms_hs_passthrough.open_cursor@FREETDS_DG4ODBC_EMGTW_11_2_0_3;
10 dbms_hs_passthrough.parse@FREETDS_DG4ODBC_EMGTW_11_2_0_3 (c, 'SELECT count(*) FROM '||dbname||'.'|| ownr || '.'||tabname||'');
11 LOOP
12 nr:= DBMS_Hs_Passthrough.fetch_row@FREETDS_DG4ODBC_EMGTW_11_2_0_3(c);
13 exit when nr=0;
14 dbms_hs_passthrough.get_value@FREETDS_DG4ODBC_EMGTW_11_2_0_3(c,1,val);
15 dbms_output.put_line(val);
16 end loop;
17 dbms_hs_passthrough.close_cursor@FREETDS_DG4ODBC_EMGTW_11_2_0_3(c);
18 end;
19 /
24576
PL/SQL procedure successfully completed.
=> instead of executing the statement using "execute Immediate" we have to use PASTHROUGH package to pass the statement to the SQL Server.
Edited by: kgronau on Jul 23, 2012 10:10 AM