我在a.cpp中query.exec(QObject::tr("select id from ib_sensors where dtu_id = %1;").arg(dtumac));
while(query.next())//查询成功
{
sensor_id = query.value(0).toInt();
qDebug()<<"sensor_id"<<sensor_id<<endl;
}
这句话是成功的,分别显示sensor_id 1sensor_id 2,.......
但是如果while(query.next())//查询成功
{
sensor_id = query.value(0).toInt();
qDebug()<<"sensor_id"<<sensor_id<<endl;
query.exec(QObject::tr("select bridge_id from ib_sensors where id = %1;").arg(sensor_id));
bridgeid = query.value(0).toInt();//全局变量bridgeid,在b.cpp调用,就会出现问题,我本意是想根据不同的sensoe_id得到不同bridgeid等等信息,遇到这种情况咋弄的
qDebug()<<"bridgeid"<<bridgeid<<endl;
}
...全文
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mysql qt 多字段匹配
我在a.cpp中query.exec(QObject::tr("select id from ib_sensors where dtu_id = %1;").arg(dtumac)); while(query.next())//查询成功 { sensor_id = query.value(0).toInt(); qDebug()<<"sensor_id"<<sensor_id<<endl; } 这句话是成功的,分别显示sensor_id 1sensor_id 2,....... 但是如果whil
QSqlQuery queryIdFromibSensors(db);
QSqlQuery queryBridgeIdFromibSensors(db);
queryIdFromibSensors.exec(QObject::tr("select id from ib_sensors where dtu_id = %1;").arg(dtumac));//根
while(query.next())//查询成功
{
int sensor_id = queryIdFromibSensors.value(0).toInt();
qDebug()<<"sensor_id"<<sensor_id<<endl;//此处运行正常,两个sensor_id 全部输出
queryBridgeIdFromibSensors.exec(QObject::tr("select bridge_id from ib_sensors where id = %1;").arg(sensor_id));
if ( queryBridgeIdFromibSensors.first() )
{
int bridgeid = queryBridgeIdFromibSensors.value(0).toInt();
qDebug()<<"bridgeid"<<bridgeid<<endl;
}
}
题外话:你的代码质量和Qt组件对数据库访问如何操作了解比较不够。
后边那段代码,你的query1都没有exec,也就是说显然没有结果集,你用第一个query的for循环拿去访问第二个query的结果集,你觉得能不出问题吗?
另外,你对数据库的SQLScript显然也不是很清楚。我看了你的脚本,根本不需要分成取两次啊,直接:
select id,sensor_id,bridge_id from ib_sensors where dtu_id=...不久可以了? 从一张表都要retrieve两次,这不是折腾吗?