QtSql connect to multiple databases

Question

I am having a problem with Python 3.7 PyQt5 QtSql. I am trying to have multiple MSSQL databases connected, but cannot figure how to do it.

I have the following function to connect:

from PyQt5 import QtSql
def connectDb(database_name):
    SERVER_NAME = 'COMPUTER\\SQLEXPRESS'
    DATABASE_NAME = database_name
    connString = f'DRIVER={{SQL Server}};'\
                 f'SERVER={SERVER_NAME};'\
                 f'DATABASE={DATABASE_NAME}'
    db = QtSql.QSqlDatabase.addDatabase("QODBC")
    db.setDatabaseName(connString)
    if not db.open():
        print(db.lastError().text())
    return db

To connect to a database:

db1 = connectDb("Database1")
db2 = connectDb("Database2")

However, when trying to connect to the second database, I get the message:

QSqlDatabasePrivate::removeDatabase: connection 'qt_sql_default_connection' is still in use, all queries will cease to work.
QSqlDatabasePrivate::addDatabase: duplicate connection name 'qt_sql_default_connection', old connection removed.

The reason I want to keep multiple databases open is that it is far too slow to keep opening and closing database connections each time I need to query a different database in my code. I'd rather keep them all open and close them when the program exits.

Answer 1

When a QSqlDataBase is created using the addDatabase() method then the names passed through the connectionName parameter are stored in a dictionary where the key takes that value, if that parameter is not passed then "qt_sql_default_connection" is used causing the creation of the Second database you get a duplicate in the dictionary so Qt issues that warning. A possible solution is to pass it a different name (not tested):

from PyQt5 import QtSql


def connectDb(database_name, connection_name):
    SERVER_NAME = "COMPUTER\\SQLEXPRESS"
    DATABASE_NAME = database_name
    connString = (
        f"DRIVER={{SQL Server}};" f"SERVER={SERVER_NAME};" f"DATABASE={DATABASE_NAME}"
    )
    db = QtSql.QSqlDatabase.addDatabase("QSQLITE", connection_name)
    db.setDatabaseName(connString)
    if not db.open():
        print(db.lastError().text())
    return db

db1 = connectDb("Database1", "connection_1")
db2 = connectDb("Database2", "connection_2")