[Tutor] Sorting Data in Databases

[spir]

"Ken G." <beachkid at insightbb.com> wrote:

> I have not use the DBMS as I am unaware of them in both languages.   

DBMS is short for Data Base Management System, see wikipedia entry on the topic.
Actually, the term is a bit ambiguous:
* From a user point of view, a BDMS will be an application allowing managing data sets in a hopefully meaningful and easy manner.
* From a programmer point of view, it will be a system for wich a binding exists in one's favorite programming language, meaning a library that that can be imported.

> Lie Ryan wrote:
> > Ken G. wrote:
> >> The way I use to do it in another programming language (Liberty Basic 
> >> in Windows) was:
> >>
> >> 1. Count number of data entry in database.
> >> 2. Dimension or create an array to equal the maximum number of entry.
> >> 3. Copy data entry from database into array.
> >> 4. Use the SORT command on array, ascending or descending sequence.
> >> 5. Copy sorted data from array into database.
> >
> > In any programming language, that was the wrong algorithm, except for 
> > very low-volume purpose. You should ask the DBMS system to sort the 
> > database whenever possible instead of doing the sorting yourself.
> >
> >>  From what I know of Python so far, is it possible to sort the 
> >> database as it or do I have to copy data into either a list, tuple or 
> >> dictionary and sort there and then, after sorting copy sorted entry 
> >> back into the database.
> >
> > Question time:
> > 1. What DBMS are you using?
> > 2. What python interface to the DBMS you are using?
> > 3. Why do you think you need to sort the database? There is no 
> > advantage (that I know of) of having a sorted database. A decent DBMS 
> > should determine how best to store the data (it's their problem, not 
> > yours). If your DBMS can't do this, you should consider using another 
> > DBMS.
> > 4. Can't you simply sort the queried data? An SQL-based DBMS should 
> > support ORDER BY command to sort the SELECT-ed rows. That should be 
> > faster than sorting the whole database. You can sort the returned 
> > tuple yourself, but it would be very difficult to beat the DBMS's 
> > ORDER BY.
> >
> >> An outline of what needed to be done will be fine so I can study and 
> >> learn the proper way of doing this in Python.  FWIW, I just finished 
> >> Alan's tutorial on list, tuple and dictionary.  Whew!!!  Quite 
> >> comprehensive.
> > As stated, I am unaware of any DBMS in both languages.  In Basic and 
> > now in Python, I wrote up a program to input data to the datafile and 
> > a program to output the content of the database.  Very primitive and 
> > basic.
> 
> All of the databases I spoke of are arranged by date and if necessary, 
> time.  One contains my blood glucose reading and it is now, the newest 
> entry is at the bottom of the database.  I need to arrange it in 
> descending order whereas I can print out a report of the last 55 entries 
> for my doctor.  Some of the entries in the other databases are not in 
> sequenced order and I wish them to be, either ascending or descending 
> sequence.  The data are numerical, ranging in the length of 20, 22 and 
> 44 long with no spaces.

I'm not sure of what order is in the file, and what order you want. Seems the data is ordered by date/time, so maybe you would like to sort last n entries by glucose rate? but it's not such clear for me.

What is clear:
* The data files are "hand-made" data recordings.
* You don't need a complicated (relational) DBMS.

If you have a bit of free time, I would advise to explore both:
* Sorting the data from files as are now (you will need to sort "records" on the proper column).
* Using the simplest possible DBMS available from python, namely I guess SQLite (correct me if I'm wrong), to replace your data storing system.

> Thank you for letting me look a little further into DBMS.
> 
> Ken




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