Improve efficiency of database connection

reezeus

Hi I have a class called "SqlConnect" that allows me to connect to an MS SQL Server. The class works well, however this class is called from dozens of other classes, and hence I need to instanciate a new object of the SqlConnect class in each of those classes.

Here is how the SqlConnect class looks like:
//Constructor:
@
SqlConnect::SqlConnect(QString dbName, QString alias){
database = QSqlDatabase::addDatabase("QODBC", alias);
database.setDatabaseName("Driver={SQL Server};Server=myServer;Database=" + dbName + ";");
database.setUserName("myUsername");
database.setPassword("myPassword");

database.open();

}
@

//Main function (to request the DB):
@
QSqlQuery SqlConnect::GetResultsFromQuery(QString command){
query = QSqlQuery(database);
query.setForwardOnly(true);
query.prepare(command);
query.exec();
return query;
}
@

Each class using the SqlConnect object is as follow:
.h:
@SqlConnect *sql;@
.cpp:
@sql = new SqlConnect("databaseName", "callingClassName");@

Since I'm connecting to only 2 different database in the whole program, I believe I could do much more efficient by having only two instances that can be used at a global scope by all the classes. I have never used global variables since it's known to be a bad practice. Could you please help me and tell me how can I use only one instance (across all my classes) of SqlConnect for each database I want to connect to.

Thanks much

SGaist

Hi,

At startup create your two connections with different names and when you want to execute a query on a given database just use:

QSqlDatabase db = QSqlDatabase::database("my connection name");
QSqlQuery query(db);
...//rest of your code

reezeus

Hi SGaist

Thanks for your help (again).
What do you mean at startup? In which class?

SGaist

Your application startup, it can be done in the main function or in a class that you see fit for that.

reezeus

Let's say I put it in the main function (which is alone in the main class in my case), then 'db' will exists only in the main function ? I have others useful function in SqlConnect like bulk insert, etc. so I really would like to keep using it..

SGaist

The db variable yes but the related connection itself no. You can retrieve it where you want using the method I mentioned above.

reezeus

Oh! My mistake I read QSqlDatabase::addDatabase instead of QSqlDatabase::database. Ok I'm trying it now.
Thanks.

reezeus

Works like a charm. Thanks much for your help.

SGaist

You're welcome !

No need to modify the title anymore, just use the "Topic Tool" button to mark the thread as solved :)

reezeus

Done :)