You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: db_select.m
    path of file: ./repos/PsPM/src/Import/fieldtrip/fileio/private
    
    the code of the file until where you have to start completion: function s = db_select(tablename, fields, sel)

% DB_SELECT selects data from a database table and converts it into a
% Matlab structure.Each of the fields in the database table will be
% represented as field in the strucure.

    
function s = db_select(tablename, fields, sel)

% DB_SELECT selects data from a database table and converts it into a
% Matlab structure.Each of the fields in the database table will be
% represented as field in the strucure.
%
% Use as
%   s = db_select(tablename, fields)
%   s = db_select(tablename, fields, num)
%
% The optional argument num allows you to select a specific row number.

% Copyright (C) 2007, Robert Oostenveld
%
% $Log: db_select.m,v $
% Revision 1.1  2007/11/07 10:50:46  roboos
% created helper functions for easy access to a MySQL database table using a structure for representing the data
%

nfields  = length(fields);
fieldstr = sprintf('%s, ', fields{:});
fieldstr = fieldstr(1:(end