Great, thank you all. I will always add "order by" when fetching data into da data frame and assume the rows in MySQL might not always be in right order
-----Ursprüngliche Nachricht----- Von: Prof Brian Ripley [mailto:rip...@stats.ox.ac.uk] Gesendet: Mittwoch, 20. November 2013 18:19 An: Enrico Schumann; Chris Cc: r-sig-db@r-project.org Betreff: Re: [R-sig-DB] RODBC sqlSave appends rows from data frame in reverse order On 20/11/2013 16:34, Enrico Schumann wrote: > On Wed, 20 Nov 2013, "Chris" <c...@incentive-investing.com> writes: > >> Hi, >> >> I append rows to a table in MySQL with sqlSave from RODBC package. >> The data frame that is saved is ordered by date ascending (first >> column) as is the table in the DB. When I send the whole data frame >> at once, the data frame is appended in reverse order. That means the >> row with the newest date in the data frame is the first row appended >> to the table, while the row with oldest date will be last row in the >> table. OK, I thought that "append" just orders by date descending and >> that is why the reverse ordering happens. But when I send each row of >> the data frame using a for-loop the result is the same: The first row >> send is the last row in the table, the second row send, is the second last row in the table. >> >> My solution is to run the for loop from last to first row of the data >> frame but I am looking for an explanation why append works like this >> and if it's possible to change this in some setting. >> > > In MySQL, you never have a guarantee in which order the rows will be > retrieved unless you specify it (eg, "SELECT * FROM table ORDER BY > column;"). Nor any other RDBMS: as the RODBC manual does say (on p.6). > > [...] > >> >> Thank you >> >> Chris >> > -- Brian D. Ripley, rip...@stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 _______________________________________________ R-sig-DB mailing list -- R Special Interest Group R-sig-DB@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-db
