[Tutor] How to write database-agnostic python code? (Is this even possible?)

[Maxime S]

2017-09-13 3:58 GMT+02:00 boB Stepp <robertvstepp at gmail.com>:

> On Tue, Sep 12, 2017 at 2:17 PM, Mats Wichmann <mats at wichmann.us> wrote:
> > On 09/12/2017 01:05 PM, boB Stepp wrote:
> >> As I continue to read about SQL, one thing jumps out:  There are many
> >> differences between how SQL statements are implemented among the
> >> different database products.  Even for relatively simple,
> >> straightforward things like field concatenation.  One DB might use
> >> "||" as the operator.  Another uses "+".  Yet another only uses a
> >> "CONCAT" function.  This is crazy!
>
> [...]
>
> > But dealing with "local extension to SQL" is a different problem.  SQL
> > is actually a standard and should work the same everywhere, but then
> > people decide they need to improve it.  Being agnostic means avoiding
> > mysql-specific syntax, postgres-specific syntax, etc.  Which means you
> > need to know what is specific in the first place...
>
> In the example I was alluding to, concatenating fields, surely this is
> a "standard SQL" query?  So, for instance, if I had a Sales table with
> FirstName and LastName fields and wanted to use SQL to get the full
> name from these:
>

Concatenation is indeed part of the ISO standard (using the || operator).

Unfortunately no DB respect the standard 100%.

There is a nice comparaison of the different behaviours here:
http://troels.arvin.dk/db/rdbms/

It is very hard to create an application that is truly DB-independent. Most
applications just pick one and then have to stick with it ever after.


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