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//! [0]
// WRONG
QSqlDatabase db = QSqlDatabase::database("sales");
QSqlQuery query("SELECT NAME, DOB FROM EMPLOYEES", db);
QSqlDatabase::removeDatabase("sales"); // will output a warning
// "db" is now a dangling invalid database connection,
// "query" contains an invalid result set
//! [0]
//! [1]
{
QSqlDatabase db = QSqlDatabase::database("sales");
QSqlQuery query("SELECT NAME, DOB FROM EMPLOYEES", db);
}
// Both "db" and "query" are destroyed because they are out of scope
QSqlDatabase::removeDatabase("sales"); // correct
//! [1]
//! [2]
QSqlDatabase::registerSqlDriver("MYDRIVER",
new QSqlDriverCreator<MyDatabaseDriver>);
QSqlDatabase db = QSqlDatabase::addDatabase("MYDRIVER");
//! [2]
//! [3]
...
db = QSqlDatabase::addDatabase("QODBC");
db.setDatabaseName("DRIVER={Microsoft Access Driver (*.mdb)};FIL={MS Access};DBQ=myaccessfile.mdb");
if (db.open()) {
// success!
}
...
//! [3]
//! [4]
...
// MySQL connection
db.setConnectOptions("CLIENT_SSL=1;CLIENT_IGNORE_SPACE=1"); // use an SSL connection to the server
if (!db.open()) {
db.setConnectOptions(); // clears the connect option string
...
}
...
// PostgreSQL connection
db.setConnectOptions("requiressl=1"); // enable PostgreSQL SSL connections
if (!db.open()) {
db.setConnectOptions(); // clear options
...
}
...
// ODBC connection
db.setConnectOptions("SQL_ATTR_ACCESS_MODE=SQL_MODE_READ_ONLY;SQL_ATTR_TRACE=SQL_OPT_TRACE_ON"); // set ODBC options
if (!db.open()) {
db.setConnectOptions(); // don't try to set this option
...
}
//! [4]
//! [5]
#include "qtdir/src/sql/drivers/psql/qsql_psql.cpp"
//! [5]
//! [6]
PGconn *con = PQconnectdb("host=server user=bart password=simpson dbname=springfield");
QPSQLDriver *drv = new QPSQLDriver(con);
QSqlDatabase db = QSqlDatabase::addDatabase(drv); // becomes the new default connection
QSqlQuery query;
query.exec("SELECT NAME, ID FROM STAFF");
...
//! [6]
//! [7]
unix:LIBS += -lpq
win32:LIBS += libpqdll.lib
//! [7]
//! [8]
QSqlDatabase db;
qDebug() << db.isValid(); // Returns false
db = QSqlDatabase::database("sales");
qDebug() << db.isValid(); // Returns true if "sales" connection exists
QSqlDatabase::removeDatabase("sales");
qDebug() << db.isValid(); // Returns false
//! [8]
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