you can use the query to merge the fields.that query will 
be executed through the sqlcommand.

You Can Write Query :

select (databasename).(owner).(tablename1).
(datafield),select (databasename).(owner).(tablename2).
(datafield) from (databasename).(owner).(tablename1),
(databasename).(owner).(tablename2)


Example:select 
LSKGROUP.dbo.addsites.state,LSKGROUP.dbo.employee.empname 
from LSKGROUP.dbo.addsites,LSKGROUP.dbo.employee

and then fill the values to new dataset table.

Remember:

if database also differ put databse's name accordingly




Good Luck.....

Consider a dataset(ds) having two datatables or we can say
that it contains data from two tables..

System.Data.DataTable dt = new DataTable();
dt.Columns.Add("Field1", typeof(string));
dt.Columns.Add("Field2", typeof(string));

if(ds.Tables[0].Rows.Count > 0)
 {
   foreach(DataRow dr in ds.Tables[0].Rows)
    {
	DrNew = dt.NewRow();
	DrNew[0] = dr["Field1"].ToString();
    }
 }

if(ds.Tables[1].Rows.Count > 0)
 {
   foreach(DataRow dr in ds.Tables[1].Rows)
    {
	DrNew = dt.NewRow();
	DrNew[0] = dr["Field2"].ToString();
    }
 }
dt.AcceptChanges();

get data from first table and add it as a column in another 
table and do the same way to retrive the second data from 
other table.Add it to third column..

DataTable dt1 = retDT("select col1,col2 from Table1");
DataTable dt2 = retDT("select col3,col4 from Table2");
dt1.Merge(dt2);

retDT is a funtion to return datatable based on the query.

The output will be like below
if you check the dt1 content then the output will be

col1 col2 col3 col4
1     2    3    4