assert start == None or isinstance(start, (int, long))

    if order_by is order_by_pkey:

        if table0 == None or distinct_on != []: order_by = None

    query = 'SELECT'

    return [sql_gen.as_Col(strings.ustr(c), table)

        for c in table_col_names(db, table, *args, **kw_args)]

    '''If no pkey, returns the first column in the table.'''

    table = sql_gen.as_Table(table)

    except StopIteration: return table_col_names(db, table, recover)[0]

def pkey_col(db, table, *args, **kw_args):

not_null_col = 'not_null_col'

def table_not_null_col(db, table, recover=None):

    '''Name assumed to be the value of not_null_col. If not found, uses pkey.'''

    if not_null_col in table_col_names(db, table, recover): return not_null_col

def constraint_cond(db, constraint):

    module = util.root_module(db.db)

    @pre The table must not already have a primary key.

    '''

    table = sql_gen.as_Table(table)

    col_strs = [sql_gen.to_name_only_col(v).to_str(db) for v in cols]

    run_query(db, 'ALTER TABLE '+table.to_str(db)+' ADD PRIMARY KEY ('

        in_tables.append(in_table)

        no_empty.add(in_table)

    # Add fkey to parent

    if parent_ids_loc != None:

        if sql_gen.is_table_col(parent_ids_loc):

            no_empty.add(parent_ids_loc.table)

        parent_ptr = node.getAttribute('fkey')

        row[parent_ptr] = parent_ids_loc

    # Parse input columns

    return pkeys_loc

def get(db, node, limit=None, start=None):

    node = node.firstChild

    table = name_of(node)

    fields = []

    conds = {}

        elif xml_dom.is_text(child): conds[child_name] = xml_dom.value(child)

        else: raise Exception('Joins not supported yet')

    id_ = xml_dom.get_id(node)

    if fields == []: fields.append(pkey_)

    return sql.select(db, table, fields, conds, limit, start)

        warnings.warn(UserWarning('Inserting empty table row(s)'))

    if is_function: out_pkey = 'result'

    out_pkey_col = sql_gen.as_Col(out_pkey, out_table)

    in_tables_ = copy.copy(in_tables) # don't modify input!

    try: in_tables0 = in_tables_.pop(0) # first table is separate

    except IndexError: in_tables0 = None

    else:

        in_pkey_col = sql_gen.as_Col(in_pkey, in_tables0)

    # Determine if can use optimization for only literal values