QT 连接多个数据库，必须指定不同的连接名字

/* QT 连接多个数据库，必须指定不同的连接名字 */

#include "q2.h"

#include <QSqlDatabase>

#include <QSqlError>

#include <QSqlQuery>

QSqlDatabase *db;

QSqlDatabase *db2;

q2::q2(QWidget *parent, Qt::WFlags flags)

: QMainWindow(parent, flags)

{

ui.setupUi(this);

db = new QSqlDatabase(QSqlDatabase::addDatabase("QMYSQL"));// 没指定连接名字，则为默认库

db->setDatabaseName("sns");

db->setHostName("127.0.0.1");

db->setPort(3306);

db->setUserName("root");

db->setPassword("");

if (! db->open()) {

QSqlError e = db->lastError();

qFatal("ServerDB db1: Failed initialization: %s",qPrintable(e.text()));

}

db2 = new QSqlDatabase(QSqlDatabase::addDatabase("QMYSQL", "db2"));// 如果要连接多个数据库，必须指定不同的连接名字，否则会覆盖上面的默认连接

db2->setDatabaseName("bbs");

db2->setHostName("127.0.0.1");

db2->setPort(3306);

db2->setUserName("root");

db2->setPassword("");

if (! db2->open()) {

QSqlError e = db2->lastError();

qFatal("ServerDB db1 : Failed initialization: %s",qPrintable(e.text()));

}

}

void q2::on_pushButton_clicked()

{

if (db->isValid())

{

QSqlQuery query;// 查默认库，即 db

if (query.prepare("select * from users"))

{

if (query.exec())

{

if (query.next())

ui.pushButton->setText(query.value(2).toString());

else

qWarning("SQL Error [%s]: %s", qPrintable(query.lastQuery()), qPrintable(query.lastError().text()));

}

else

{

qWarning("SQL Error [%s]: %s", qPrintable(query.lastQuery()), qPrintable(query.lastError().text()));

}

}

else

{

qWarning("SQL Error [%s]: %s", qPrintable(query.lastQuery()), qPrintable(query.lastError().text()));

}

}

else

{

qWarning("SQL rejected: Database is gone");

}

}

void q2::on_pushButton_2_clicked()

{

if (db2->isValid())

{

QSqlQuery query(*db2);// 查另一个数据库 db2

if (query.prepare("select * from users"))

{

if (query.exec())

{

if (query.next())

ui.pushButton_2->setText(query.value(2).toString());

else

qWarning("SQL Error [%s]: %s", qPrintable(query.lastQuery()), qPrintable(query.lastError().text()));

}

else

{

qWarning("SQL Error [%s]: %s", qPrintable(query.lastQuery()), qPrintable(query.lastError().text()));

}

}

else

{

qWarning("SQL Error [%s]: %s", qPrintable(query.lastQuery()), qPrintable(query.lastError().text()));

}

}

else

{

qWarning("SQL rejected: Database is gone");

}

}

q2::~q2()

{

db->close();

delete db;

db = NULL;

db2->close();

delete db2;

db2 = NULL;

}