Generic function to display a specific row from any table

Question

Hi all,
I need some help to write a function in PL/SQL or Dynamic SQL (or both), to write a function that would take in parameters only the unique ID of the row to display and the name of the table to display (that could be any table with any format).
Actually we don't know in advance which table will be accessed, so we don't know the columns and their types until the function is called.
Once I get the row, I want to return a small table with a size of only one line containing the details of the row I looked for.
So the signature of the function would be something like: CREATE function displayDetailedRowFromAnyTable(uniqId in varchar2(25), tableName in varchar2(25)).
Hope the description is clear. I found in some forums some details about this kind of problems; however, the structure of the tables (ie. the columns name and their types) is always known in advance. In my case, I don't know those details until run time.
Any help would be greatly appreciated.

Answer 1

There is a built in "function" to do this. It's called "SELECT" and it's available through the SQL engine. You give it the table name and the ID you want and it can return you all the columns from that table...
e.g.
SELECT *
FROM <table_name>
WHERE id = <required_id>If you truly want a generic dynamic SQL then you'll have to code it as an ANYTYPE (as already mentioned above). Although this will make your code very complex and difficult to maintain.
e.g. of defining your own dynamic pipelined function using anytype ...
create or replace type NColPipe as object
  l_parm varchar2(10),   -- The parameter given to the table function
  rows_requested number, -- The parameter given to the table function
  ret_type anytype,      -- The return type of the table function
  rows_returned number,  -- The number of rows currently returned by the table function
  static function ODCITableDescribe( rtype out anytype, p_parm in varchar2, p_rows_req in number := 1 )
  return number,
  static function ODCITablePrepare( sctx out NColPipe, ti in sys.ODCITabFuncInfo, p_parm in varchar2, p_rows_req in number := 1 )
  return number,
  static function ODCITableStart( sctx in out NColPipe, p_parm in varchar2, p_rows_req in number := 1 )
  return number,
  member function ODCITableFetch( self in out NColPipe, nrows in number, outset out anydataset )
  return number,
  member function ODCITableClose( self in NColPipe )
  return number,
  static function show( p_parm in varchar2, p_rows_req in number := 1 )
  return anydataset pipelined using NColPipe
create or replace type body NColPipe as
  static function ODCITableDescribe( rtype out anytype, p_parm in varchar2, p_rows_req in number := 1 )
  return number
  is
    atyp anytype;
  begin
    anytype.begincreate( dbms_types.typecode_object, atyp );
    atyp.addattr( to_char(to_date(p_parm,'MONYYYY'),'MONYY')
                , dbms_types.typecode_varchar2
                , null
                , null
                , 10
                , null
                , null
    atyp.endcreate;
    anytype.begincreate( dbms_types.typecode_table, rtype );
    rtype.SetInfo( null, null, null, null, null, atyp, dbms_types.typecode_object, 0 );
    rtype.endcreate();
    return odciconst.success;
  exception
    when others then
      return odciconst.error;
  end;  
  static function ODCITablePrepare( sctx out NColPipe, ti in sys.ODCITabFuncInfo, p_parm in varchar2, p_rows_req in number := 1 )
  return number
  is
    elem_typ sys.anytype;
    prec pls_integer;
    scale pls_integer;
    len pls_integer;
    csid pls_integer;
    csfrm pls_integer;
    tc pls_integer;
    aname varchar2(30);
  begin
    tc := ti.RetType.GetAttrElemInfo( 1, prec, scale, len, csid, csfrm, elem_typ, aname );
    sctx := NColPipe( p_parm, p_rows_req, elem_typ, 0 );
    return odciconst.success;
  end;
  static function ODCITableStart( sctx in out NColPipe, p_parm in varchar2, p_rows_req in number := 1 )
  return number
  is
  begin
    return odciconst.success;
  end;
  member function ODCITableFetch( self in out NColPipe, nrows in number, outset out anydataset )
  return number
  is
  begin
    anydataset.begincreate( dbms_types.typecode_object, self.ret_type, outset );
    for i in self.rows_returned + 1 .. self.rows_requested
    loop
      outset.addinstance;
      outset.piecewise();
      outset.setvarchar2( self.l_parm );
      self.rows_returned := self.rows_returned + 1;
    end loop;
    outset.endcreate;
    return odciconst.success;
  end;
  member function ODCITableClose( self in NColPipe )
  return number
  is
  begin
    return odciconst.success;
  end;
end;
And to use it
SQL> select * from table( NColPipe.show( 'JAN2008' ) );
JAN08
JAN2008