Having trouble with setRelation

[A Former User]

I have a database with a few tables. I'm trying to use two of the tables in a relational setting. Here are the queries that create the tables:

query = "CREATE TABLE IF NOT EXISTS recipe_names("
            "name_id INTEGER PRIMARY KEY AUTOINCREMENT, "
            "r_name VARCHAR(35));";

query1 ="CREATE TABLE IF NOT EXISTS recipe_ingredients("
            "ingredient_id INTEGER PRIMARY KEY AUTOINCREMENT, "
            "name_id INTEGER,"
            "ingredient VARCHAR(35),"
            "amount FLOAT);";

And this is the code I'm using, code I got from a youtube video (around 6 mins into the vid)

model = new QSqlRelationalTableModel(this);
model->setTable("recipe_names");
model->setRelation(0,QSqlRelation("recipe_ingredients","name_id","name"));
model->select();

I've also viewed the Qt Docs concerning relational tables, but I just don't get it. Setting this up in Delphi is a piece of cake. Not so much with Qt.

Using my two tables, can someone help me? Thanks.

[mrjj]

Hi
So it says that
recipe_names col 0 is key to recipe_ingredients mapped via
name_id and should show recipe_ingredients "name" col.
But i dont see it has a name col.
Even if i read it reversed, there is only r_name ?

[A Former User]

I changed

model->setRelation(0,QSqlRelation("recipe_ingredients","name_id","name"));

to

model->setRelation(0,QSqlRelation("recipe_ingredients","name_id","ingredients"));

I get the same thing. A blank TableView. I don't understand what I'm supposed to be doing. I use a lot of tables in my programming, most of them relationally connected. I use Delphi and Lazarus for this. And it's simple to do. But the way to do the same in Qt is strange. I just don't get it.

[KillerSmath]

@landslyde

I changed
model->setRelation(0,QSqlRelation("recipe_ingredients","name_id","name"));
to
model->setRelation(0,QSqlRelation("recipe_ingredients","name_id","ingredients"));

Replace ingredients by ingredient, because "ingredients" is not a column of recipe_ingredients.

[A Former User]

Yeah. I was in a hurry, late for a doctor appt when I put that in. However, it changed nothing. I hope the pic I'm putting in here shows up.

I tried several combinations last night before going to sleep. I can't find anything that Qt accepts to make this work.

I embedded a pic here, but it doesn't show. Here's the link to it: https://imgur.com/qEFn8On

[SGaist]

Hi,

Your database path is relative, Therefore, unless you copied the database file in the build folder, your application will just create a new empty database. This has nothing to do with Qt, it is how SQLite works.

[A Former User]

That's embarrassing. Thanks, SGaist.

I copied the same-nameed db over to the debug folder where this project is and it works as expected. Thank you.

[KillerSmath]

@SGaist mentioned

Your database path is relative, Therefore, unless you copied the database file in the build folder, your application will just create a new empty database.

@landslyde, you could use the path using the relative path of your application, similar:

#include <QCoreApplication>
...
db.setDatabaseName(QCoreApplication::applicationDirPath()+"/zyx.db");

[A Former User]

Thanks for the help, Forum.

[SGaist]

QStandardPaths is also worth taking a look at.

[A Former User]

@SGaist - good information. Thank you.