* @param columns a array with one or more DBColumn objects
*/
public void setPrimaryKey(DBColumn... columns)
{
if (columns==null || columns.length==0)
throw new InvalidArgumentException("columns", columns);
// All columns must belong to this table
for (int i=0; i<columns.length; i++)
if (columns[i].getRowSet()!=this)
throw new InvalidArgumentException("columns["+String.valueOf(i)+"]", columns[i].getFullName());
// Set primary Key now
primaryKey = new DBIndex(name + "_PK", DBIndex.PRIMARYKEY, columns);
indexes.add(primaryKey);
primaryKey.setTable(this);
}