Re: looking but not finding

On Thu, Jul 13, 2023 at 12:04 PM Dennis Lee Bieber
<[email protected]> wrote:
>
> On Wed, 12 Jul 2023 17:59:45 -0500, o1bigtenor <[email protected]>
> declaimed the following:
>
>
> >Spent some time looking to see the difference between regular and irregular
> >data - - - another set of terms used commonly and just not defined!
> >(Or at least not well or perhaps only hard to find!)
>
>         "Regular", as used here, means that EVERY record has the same layout.
> You may have columns that permit NULLs, but all the columns are in each
> record, and the columns are in the same order from record to record.
> Classic relational database theory (besides SQL, you'd want to study the
> first three Codd Normal Forms -- short summary, not in NF order: no column
> has repeating data; if you did have repeating data it gets split into a
> second relation with a foreign key [link] back to the parent relation
> unique ID, and if order matters, a sequence value added to the second
> relation for sorting; all data should be dependent upon the primary key, if
> you find you are repeating the same information over and over it should go
> into another relation and link to it replaces the column(s) in the main
> relation}
>
Thank you for this definition!!!!

> uniqueID | timestamp | sensornumber | sensorreading | etc.
>
> {My practice is to always put an auto-incrementing ID field, even if
> [timestamp|sensornumber] might be sufficient to uniquely identify one
> reading}
>
>         At the most gross level, irregular data would be a system that might
> store a Word document next to an Excel spreadsheet next to... There is no
> regularity (no tabular representation) of the data. Some such may be
> described as "document" databases.
>
> Per https://en.wikipedia.org/wiki/MongoDB MongoDB is a document oriented
> system using JSON format "documents"
>
> https://en.wikipedia.org/wiki/Zope_Object_Database ZODB is a persistence
> scheme for Python objects -- uses pickle so essentially only Python code
> can read/write the contents.

Excellent - - - and now I can understand where MongoDB might be useful.
>
>         SQLite, (Windows) Access/JET, M$ SQL Server, MySQL/MariaDB, Oracle,
> PostgreSQL, Firebird are all relational database management systems. Most
> offer command line tools for simple queries. SQLite and Access/JET are
> "file server" RDBMs -- your code actually links to the database runtime and
> directly opens the database files. SQL Server, MySQL/MariaDB, Oracle,
> PostgreSQL, and Firebird are "client/server" RDBMs -- there is a
> server/engine running on some machine which is responsible for opening the
> database files, and your code sends SQL statement to that server for
> processing.
>
Great - - - thank you very much!!!

Regards
_______________________________________________
Tutor maillist  -  [email protected]
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor