def query_and(*queries):
    """
    Given multiple queries it joins them using the & operator.

    Examples
    --------
    .. doctest::
        >>> from limix.data import query_and
        >>>
        >>> query1 = 'a < b'
        >>> query2 = 'b >= c'
        >>> query3 = 'c == 1'
        >>> query = query_and(query1, query2, query3)
        >>>
        >>> print(query)
        a < b & b >= c & c == 1
    """
    if len(queries) >= 1:
        query = ' & '.join(queries)
    else:
        query = None
    return query