Can I access sqlite3 using octave?

问题

Is there a way to read and write to sqlite3 from octave?

I'm thinking something along the lines of RODBC in R or the sqlite3 package in python, but for octave.

I looked on octave-forge http://octave.sourceforge.net/packages.php

But could only find the 'database' package, which only supports postgresql.

Details:

OS: Ubuntu 12.04
Octave: 3.6.2
sqlite: 3.7.9

回答1:

I realise this is an old question, but most answers here seem to miss the point, focusing on whether there exists a bespoke octave package providing a formal interface, rather than whether it is possible to perform sqlite3 queries from within octave at all in the first place.

Therefore I thought I'd provide a practical answer for anyone simply trying to access sqlite3 via octave; it is in fact trivial to do so, I have done so myself many times.

Simply do an appropriate system call to the sqlite3 command (obviously this implies you have an sqlite3 client installed on your system). I find the most convenient way to do so is to use the

sqlite3 database.sqlite < FileContainingQuery > OutputToFile

syntax for calling sqlite3.

Any sqlite3 commands modifying output can be passed together with the query to obtain the output in the desired format.

E.g. here's a toy example plotting a frequency chart from a table which returns appropriate scores and counts in csv format (with headers and runtime stats stripped from the output).

  pkg load io   % required for csv2cell (used to collect results)

% Define database and Query
  Database = '/absolute/path/to/database.sqlite';

  Query = strcat(
  % Options to sqlite3 modifying output format:
    ".timer off            \n",   % Prevents runtime stats printed at end of query
    ".headers off          \n",   % If you just want the output without headers
    ".mode csv             \n",   % Export as csv; use csv2cell to collect results
  % actual query
    "SELECT Scores, Counts \n",
    "FROM Data;            \n"    % (Don't forget the semicolon!)
  );   

% Create temporary files to hold query and results
  QueryFile   = tempname()  ;   QueryFId = fopen( QueryFile, 'w' );
  fprintf( QueryFId, Query );   fclose(  QueryFId);
  ResultsFile = tempname();

% Run query
  Cmd = sprintf( 'sqlite3 "%s" < "%s" > "%s"',  Database, QueryFile, ResultsFile );
  [Status, Output] = system( Cmd );

% Confirm query succeeded and if so collect Results
% in a cell array and clean up temp files.
  if Status != 0,     delete( QueryFile, ResultsFile ); error("Query Failed");
  else,   Results = csv2cell( ResultsFile ); delete( QueryFile, ResultsFile );
  end

% Process Results
  Results  = cell2mat( Results );
  Scores   = Results(:, 1);   Counts  = Results(:, 2);
  BarChart = bar( Scores, Counts, 0.7 ); % ... etc

Et, voilà

回答2:

According to Octave-Forge the answer is no.

Interface to SQL databases, currently only postgresql using libpq.

But you can write your own database package using the Octave C++ API with SQLite C API

回答3:

As you already found out, the new version of the database package (2.0.0) only supports postgreSQL. However, old versions of the package also supported MySQL and SQLite (the last version with them was version 1.0.4).

Its problem is that the old database packages do not work with the new Octave and SWIG versions (I think the last version of Octave where the database package worked was 3.2.4). Aside the lack of maintainer (package was abandoned for almost 4 years) its use of SWIG was becoming a problem since it made more difficult for other developers to step in. Still, some users tried to fix it and some half fixes have been done (but never released). See bug #38098 and Octave's wiki page on the database package for some reports on making it work with SQLite in Octave 3.6.2.

The new version of the package is a complete restart of the package. Would be great if you could contribute with development for SQLite bindings.

回答4:

Check out this link http://octave.1599824.n4.nabble.com/Octave-and-databases-td2402806.html which asks the same question regarding MySQL.

In particular this reply from Martin Helm points the way to using JDBC to connect to any JDBC supported database - "Look at the java bindings in the octave java package (octave-forge), it is maintained and it works. Java is very strong and easy for database handling. Use that and jdbc driver for mysql to connect to mysql (or with the appropriate jdbc friver everything else which you can imagine). That is what I do when using db queries from octave. Much easier and less indirect than invoking scripts and parsing output from databse queries.

As far as I remeber the database package is somehow broken (at least I never was able to use it). "