QSqlDatabase - save/retrieve database to/from hard disk

[simozz]

Hi all,

I want to gain some experience with QT and database so I am studyng the Books example

https://doc.qt.io/qt-5.11/qtsql-books-example.html

My question is: would it possible to store that current database to hard disk, and retrieve it later after a program restart ?
If so, what QT's class shold I use or what is the preferred way to achieve this ?

Thank you.
Regards,
s.

[jsulm]

@simozz Use SQLite as database for that - it is file based and supported by Qt.

[mrjj]

Hi
To add to @jsulm
The reason its not saved to disk with that example is that in
books/initdb.h, function
QSqlError initDb()
{
QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
db.setDatabaseName(":memory:");

its set to be in memory
So you can change that to a file path and it will be stored on disk.

   db.setDatabaseName("c:\\somefolder\\dbname.db");

[simozz]

Hello again and thank you for the quick replies !

@jsulm Thanks, I will study better SQLite.

@mrjj Good to know your suggestion.
But what if the file already exists ?

Do the function

db.setDatabaseName("c:\\somefolder\\dbname.db");

will overwrite the dbname.db content ?
I suppose it will not and I will have to check for already existing records.
Do you confirm ?

Thanks.
s

[mrjj]

@simozz said in QSqlDatabase - save/retrieve database to/from hard disk:

setDatabaseName

Hi. it won't override as you would normally set it to open existing
DB and only in case the file not exist, it will be created.
Also, a DB can have multiple tables and hence if you want to clear all
records, you have to do that manually with SQL.

[simozz]

Thank yoy @mrjj

[mrjj]

@simozz
Hi
Just a small note.
You can use
qApp->applicationDirPath();
to get the path where exe is. Normally that is in the build folder. ( when you develop)
So you can use this to have a path to the DB that is always valid.
even on other machine.