QSqlDatabase retrieve connection in different form

[avpro]

I'm not sure if I understand.

using the database reference you retrieved at line three.

that's what I'm trying to do, just to use the recall of database connection.

Or, you can create the database connection (i.e addDatabase()) in the first place without a name making it the default connection and all subsequent QSqlQuery objects will associate with that by default.

I'm aware about this option. i think using a connection name is safer. it leaves no space for potential error.

When you call addDatabase() multiple times you ...

I'm not calling addDatabase multiple times. Is just once in 1.cpp line 3.

No, you are still missing the point. The QSqlQuery at line 10 should be created thus:
Qt Code:
QSqlQuery q1(addConn);

I tried and is not recognizing the addConn. error: adConn was not declared in this scope.

i tried

QSqlQuery q1("addConn")

QSqlQuery q1("addConn")

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and gives me the below error:

QSqlQuery::exec: database not open
QSqlQuery:repare: database not open
Query Error: "Driver not loaded Driver not loaded"
QSqlDatabasePrivate::removeDatabase: connection 'adUserConn' is still in use, all queries will cease to work.

the only solution working is the one described in post 14.

i will remove the

QSqlDatabase::removeDatabase("addConn");

QSqlDatabase::removeDatabase("addConn");

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, close the database connection with

addUser.database("addConn").close();

addUser.database("addConn").close();

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and

leaving clean up for program exit.

I wait and see if other errors strike against the current one. thanks for your support.

[ChrisW67]

I'm not calling addDatabase multiple times. Is just once in 1.cpp line 3.

Yes you are, once every time on_addUser_triggered() is called.

I tried and is not recognizing the addConn. error: adConn was not declared in this scope.

Sorry, my bad. I meant addUser, the reference you retrieve at line 3 of the second listing.

i tried

QSqlQuery q1("addConn")

QSqlQuery q1("addConn")

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and gives me the below error:

The QSqlQuery constructor that takes a QString argument is expecting an SQL query and optionally a reference to a database connection, not the name of a database connection. It is interpreting "adConn" as a query on the default database connection. There is no default database connection, hence the error.

i will remove the

QSqlDatabase::removeDatabase("addConn");

QSqlDatabase::removeDatabase("addConn");

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,

Good this will remove some of the run time warnings.

close the database connection with

addUser.database("addConn").close();

addUser.database("addConn").close();

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You can close the connection to the database with:

addUser.close();

addUser.close();

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Just as you did in Listing 2. This does not remove the connection definition known by the name "addConn", which remains available for use. The connection will be reopened by default the next time you do something like this:

QSqlDatabase db = QSqlDatabase::database("addConn");

QSqlDatabase db = QSqlDatabase::database("addConn");

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anywhere in your program. You can suppress the automatic open() but that is not broadly useful.

In short:

• addDatabase() defines the existence of a database of a certain type to the program and loads a plugin to suit.
• removeDatabase() completely closes and forgets a previously defined database.
• database() retrieves a reference to a database connection so you can use it
• open() opens the connection to a defined database
• close() close the connection to a defined database.