Foreign key table primary key table

/// <Summary>
/// Query Method
/// </Summary>
/// <Param name = "tabnames"> tablename </param>
/// <Returns> dataset </returns>
Public dataset query (string tabnames, string columnname)
{
Using (oraclehelper orahp = new oraclehelper ())
{
String [] tabs = tabnames. Split (',');
Dataset DATA = new dataset ();
Orahp. open ();
For (INT I = 0; I <tabs. length; I ++)
{
String tabtemp = tabs [I];
String SQL = "select nvl (v. foreign key table, '"+ tabtemp +"') as foreign key table, AC. column_name column name, AC. data_type, AC. data_length, V. primary Key table, V. primary Key column, P. primary Key column PK, V. multiple options: AC. nullable from ";
SQL + = "(select S. table_name, S. column_name, S. data_type, S. data_length, S. nullable from all_tab_columns s where ";
If (columnname. length> 0)
SQL + = "S. column_name = '" + columnname + "'";
Else
SQL + = "S. column_name <> 'objectid '";
SQL + = "and S. Owner = '" + dbowner + "' and S. table_name = '" + tabtemp + "') ac ";
SQL + = "left Outer Join (select * From view_fk where foreign key table = '" + tabtemp + "') V on V. Foreign key column = ac. column_name ";
SQL + = "left Outer Join (select * From view_pk where table name = '" + tabtemp + "') P on AC. column_name = P. Primary Key column ";
If (columnname. Length <1)
SQL + = "Union select v. foreign key table, V. as column name of the foreign key column, 'varchar2' as type, 100 as length, V. primary Key table, V. primary Key column, null as PK, V. multiple options: 'n' as nullable from (select * From view_fk where primary key table = '"+ tabtemp +"') V ";

Oraclecommand comd = new oraclecommand (SQL );
Datatable datatab = new datatable ();
Datatab. tablename = tabtemp;
If (data. Tables. Contains (tabtemp ))
Continue;
Orahp. Execute (comd, datatab );
// Data. Tables. Add (datatab );
Data = changedt (datatab );
}
Orahp. Close ();

Return data;
}
}