[Interest] How to deal with database specific syntax

[pmqt71]

My app does basic CRUD  operations, and most of them already are compatible
with different DBs.
I just have problems in WHERE conditions when using date functions. A part
from this, anything works well.
Also the binding of dates and datetimes are well supported.
So, let me say, Qt covers 90% of basic CRUD operations for any SQL DB.
I know it's not a Qt problem but an SQL problem, but I'd like some Qt
pseudofunctions, eg QT_DATEDIFF, that the driver would translate in the
specific SQL.
Qt would have full support for CRUD operations DB indipendent.
What do you think about?

pm




2015-02-12 9:30 GMT+01:00 André Somers <andre at familiesomers.nl>:

> Dmitriy Purgin schreef op 12-2-2015 om 08:04:
> > Exactly, that's what I meant by "supporting the stored procedure call
> > syntax". Sorry, it was a bit vague. Anyway, in this case you're
> > implementing a single interface for an SP call backed by multiple
> > "syntax handlers" which is much easier than handling lots of syntactic
> > differences for any kind of operations one might want to do with a
> > database. It's not ideal, it has its drawbacks but it also has
> > advantages. Moreover, pmqt71 has explicitly stated that he/she doesn't
> > want to go the ORM way.
>
> Normally in Qt, if you want to write db independent code, you have to
> create your queries using the QSqlDriver::sqlStatement method. Ignore
> the comment in the documentation that states "This class should not be
> used directly. Use QSqlDatabase instead.", as QSqlDatabase does not
> provide this API.
>
> The basic problem is however that the Qt SQL drivers are really limited.
> They only support the basics of the DML and some TCL, but they don't do
> any more advanced things, including any DDL or indeed support for stored
> procedures. They also don't support functions you can use in SQL
> statements in database. So, there simply is no support for creating
> anything more advanced than a simple insert or select query.
>
> A couple of years back, I wrote an extension to the Qt SQL drivers to
> add DDL support for a database agnostic application, and that extended
> the sqlStatement virtual method with many more features. It proved
> possible to do without modifying Qt itself, and it removed any database
> specific code I had in the application itself. Everything was abstracted
> into a new set of extended drivers. You may be able to do the same for
> accessing stored procedures in different database. If you are
> interested, I can point you to the code.
>
> André
>
>
>
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