C++ QSqlDatabase::driver方法代码示例

void sql_intro_snippets()
{
    {
//! [26]
    QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
    db.setHostName("bigblue");
    db.setDatabaseName("flightdb");
    db.setUserName("acarlson");
    db.setPassword("1uTbSbAs");
    bool ok = db.open();
//! [26]
    Q_UNUSED(ok);
    }

    {
//! [27]
    QSqlDatabase firstDB = QSqlDatabase::addDatabase("QMYSQL", "first");
    QSqlDatabase secondDB = QSqlDatabase::addDatabase("QMYSQL", "second");
//! [27]
    }

    {
//! [28]
    QSqlDatabase defaultDB = QSqlDatabase::database();
//! [28] //! [29]
    QSqlDatabase firstDB = QSqlDatabase::database("first");
//! [29] //! [30]
    QSqlDatabase secondDB = QSqlDatabase::database("second");
//! [30]
    }

    {
    // SELECT1
//! [31]
    QSqlQuery query;
    query.exec("SELECT name, salary FROM employee WHERE salary > 50000");
//! [31]

//! [32]
    while (query.next()) {
        QString name = query.value(0).toString();
        int salary = query.value(1).toInt();
        qDebug() << name << salary;
    }
//! [32]
    }

    {
    // FEATURE
//! [33]
    QSqlQuery query;
    int numRows;
    query.exec("SELECT name, salary FROM employee WHERE salary > 50000");

    QSqlDatabase defaultDB = QSqlDatabase::database();
    if (defaultDB.driver()->hasFeature(QSqlDriver::QuerySize)) {
        numRows = query.size();
    } else {
        // this can be very slow
        query.last();
        numRows = query.at() + 1;
    }
//! [33]
    }

    {
    // INSERT1
//! [34]
    QSqlQuery query;
    query.exec("INSERT INTO employee (id, name, salary) "
               "VALUES (1001, 'Thad Beaumont', 65000)");
//! [34]
    }

    {
    // NAMED BINDING
//! [35]
    QSqlQuery query;
    query.prepare("INSERT INTO employee (id, name, salary) "
                  "VALUES (:id, :name, :salary)");
    query.bindValue(":id", 1001);
    query.bindValue(":name", "Thad Beaumont");
    query.bindValue(":salary", 65000);
    query.exec();
//! [35]
    }

    {
    // POSITIONAL BINDING
//! [36]
    QSqlQuery query;
    query.prepare("INSERT INTO employee (id, name, salary) "
                  "VALUES (?, ?, ?)");
    query.addBindValue(1001);
    query.addBindValue("Thad Beaumont");
    query.addBindValue(65000);
    query.exec();
//! [36]
    }

//.........这里部分代码省略.........

QDjangoCompiler::QDjangoCompiler(const char *modelName, const QSqlDatabase &db)
{
    driver = db.driver();
    baseModel = QDjango::metaModel(modelName);
}

QSqlDatabase Database::Connect() {
  QMutexLocker l(&connect_mutex_);

  // Create the directory if it doesn't exist
  if (!QFile::exists(directory_)) {
    QDir dir;
    if (!dir.mkpath(directory_)) {
    }
  }

  const QString connection_id = QString("%1_thread_%2").arg(connection_id_).arg(
      reinterpret_cast<quint64>(QThread::currentThread()));

  // Try to find an existing connection for this thread
  QSqlDatabase db = QSqlDatabase::database(connection_id);
  if (db.isOpen()) {
    return db;
  }

  db = QSqlDatabase::addDatabase("QSQLITE", connection_id);

  if (!injected_database_name_.isNull())
    db.setDatabaseName(injected_database_name_);
  else
    db.setDatabaseName(directory_ + "/" + kDatabaseFilename);

  if (!db.open()) {
    app_->AddError("Database: " + db.lastError().text());
    return db;
  }

  // Find Sqlite3 functions in the Qt plugin.
  StaticInit();

  {

#ifdef SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER
    // In case sqlite>=3.12 is compiled without -DSQLITE_ENABLE_FTS3_TOKENIZER (generally a good idea 
    // due to security reasons) the fts3 support should be enabled explicitly.
    // see https://github.com/clementine-player/Clementine/issues/5297
    //
    // See https://www.sqlite.org/fts3.html#custom_application_defined_tokenizers
    QVariant v = db.driver()->handle();
    if (v.isValid() && qstrcmp(v.typeName(), "sqlite3*") == 0) {
      sqlite3* handle = *static_cast<sqlite3**>(v.data());
      if (!handle || sqlite3_db_config(handle, SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER, 1, nullptr) != SQLITE_OK) {
        qLog(Fatal) << "Failed to enable FTS3 tokenizer";
      }
    }
#endif

    QSqlQuery set_fts_tokenizer("SELECT fts3_tokenizer(:name, :pointer)", db);
    set_fts_tokenizer.bindValue(":name", "unicode");
    set_fts_tokenizer.bindValue(
        ":pointer", QByteArray(reinterpret_cast<const char*>(&sFTSTokenizer),
                               sizeof(&sFTSTokenizer)));
    if (!set_fts_tokenizer.exec()) {
      qLog(Warning) << "Couldn't register FTS3 tokenizer";
    }
    // Implicit invocation of ~QSqlQuery() when leaving the scope
    // to release any remaining database locks!
  }

  if (db.tables().count() == 0) {
    // Set up initial schema
    qLog(Info) << "Creating initial database schema";
    UpdateDatabaseSchema(0, db);
  }

  // Attach external databases
  for (const QString& key : attached_databases_.keys()) {
    QString filename = attached_databases_[key].filename_;

    if (!injected_database_name_.isNull()) filename = injected_database_name_;

    // Attach the db
    QSqlQuery q("ATTACH DATABASE :filename AS :alias", db);
    q.bindValue(":filename", filename);
    q.bindValue(":alias", key);
    if (!q.exec()) {
      qFatal("Couldn't attach external database '%s'",
             key.toAscii().constData());
    }
  }

  if (startup_schema_version_ == -1) {
    UpdateMainSchema(&db);
  }

  // We might have to initialise the schema in some attached databases now, if
  // they were deleted and don't match up with the main schema version.
  for (const QString& key : attached_databases_.keys()) {
    if (attached_databases_[key].is_temporary_ &&
        attached_databases_[key].schema_.isEmpty())
      continue;
    // Find out if there are any tables in this database
    QSqlQuery q(QString(
                    "SELECT ROWID FROM %1.sqlite_master"
                    " WHERE type='table'").arg(key),
                db);
//.........这里部分代码省略.........

bool DbRecepient::saveToFile( QSqlDatabase memdb, QString filename, bool save )
{
    bool state = false;
    QVariant v = memdb.driver()->handle();
    if( v.isValid() && qstrcmp(v.typeName(),"sqlite3*") == 0 )
    {
        // v.data() returns a pointer to the handle
        sqlite3 * handle = *static_cast<sqlite3 **>(v.data());
        if( handle != 0 ) // check that it is not NULL
        {
            sqlite3 * pInMemory = handle;
            QByteArray array = filename.toUtf8();

            const char * zFilename = array.data();
            int rc;                   /* Function return code */
            sqlite3 *pFile;           /* Database connection opened on zFilename */
            sqlite3_backup *pBackup;  /* Backup object used to copy data */
            sqlite3 *pTo;             /* Database to copy to (pFile or pInMemory) */
            sqlite3 *pFrom;           /* Database to copy from (pFile or pInMemory) */

            /* Open the database file identified by zFilename. Exit early if this fails
            ** for any reason. */
            rc = sqlite3_open( zFilename, &pFile );
            if( rc==SQLITE_OK ){

              /* If this is a 'load' operation (isSave==0), then data is copied
              ** from the database file just opened to database pInMemory.
              ** Otherwise, if this is a 'save' operation (isSave==1), then data
              ** is copied from pInMemory to pFile.  Set the variables pFrom and
              ** pTo accordingly. */
              pFrom = ( save ? pInMemory : pFile);
              pTo   = ( save ? pFile     : pInMemory);

              /* Set up the backup procedure to copy from the "main" database of
              ** connection pFile to the main database of connection pInMemory.
              ** If something goes wrong, pBackup will be set to NULL and an error
              ** code and  message left in connection pTo.
              **
              ** If the backup object is successfully created, call backup_step()
              ** to copy data from pFile to pInMemory. Then call backup_finish()
              ** to release resources associated with the pBackup object.  If an
              ** error occurred, then  an error code and message will be left in
              ** connection pTo. If no error occurred, then the error code belonging
              ** to pTo is set to SQLITE_OK.
              */
              pBackup = sqlite3_backup_init(pTo, "main", pFrom, "main");
              if( pBackup ){
                (void)sqlite3_backup_step(pBackup, -1);
                (void)sqlite3_backup_finish(pBackup);
              }
              rc = sqlite3_errcode(pTo);
            }

            /* Close the database connection opened on database file zFilename
            ** and return the result of this function. */
            (void)sqlite3_close(pFile);

            if( rc == SQLITE_OK ) state = true;
        }
    }
    return state;
}