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QSqlQuery::value: not positioned on a valid record [复制链接]

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离线zq123456

只看楼主正序阅读楼主发表于: 2011-07-31

关键词： QString 数据 not exec ini

   两个数据表的声明如下：
query.exec(QObject::tr("create table users (Uid int primary key,"                               "Uname varchar(10))"));    query.exec(QObject::tr("insert into users values(0,'katy')"));    query.exec(QObject::tr("insert into users values(1,'cindy')"));    query.exec(QObject::tr("insert into users values(2,'小王')"));

    query.exec(QObject::tr("create table DM (DMid int primary key,"                           "Uid int"                           "FBG float not null,"                           "PBG float not null)"));    query.exec(QObject::tr("insert into DM  values(1,1,'10','20')"));
void Widget::on_pushButton_clicked(){    QSqlQuery query;    QString name=(ui->lineEdit->text());    struct userstruct id=us->selectusers(name);    qDebug()<<id.Uid<<id.Uname;}void Widget::on_pushButton_2_clicked(){    QSqlQuery query;    QString name=(ui->lineEdit_2->text());    struct hypertensionstruct id=us->selecthypertension(name);    qDebug()<<id.HPid<<id.Uid<<id.highPressure<<id.lowPressure;}

为什么第一张表能查出来，第二张表的却只能是QSqlQuery::value: not positioned on a valid record！！！！！！求高手求救，急急急！！！

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离线dongchen

只看该作者 10楼发表于: 2012-12-06

楼主的问题解决没有我也出现相同的情况了。

离线wxj120bw

只看该作者 9楼发表于: 2011-08-02

回 8楼(zq123456) 的帖子

重新编译下或者selectusers函数的query.next(); 注销掉

离线zq123456

只看该作者 8楼发表于: 2011-08-02

一样的

离线wxj120bw

只看该作者 7楼发表于: 2011-08-01

selecthypertension函数//query.next(); 注释去掉。看下效果

离线zq123456

只看该作者 6楼发表于: 2011-08-01

没什么不一样啊，select()弄出来也一样诶，我太郁闷了，我建了几张表，可是只有第一张的数据能查出来，其他几张表的估计都没有写进数据库里，都无法查出

离线wxj120bw

只看该作者 5楼发表于: 2011-08-01

你发现 selecthypertension函数和selectusers函数有什么不一样吗

离线zq123456

只看该作者 4楼发表于: 2011-08-01

struct hypertensionstruct
{int HPid;
int Uid;
QString highPressure;
QString lowPressure;
};

struct hypertensionstruct users::selecthypertension(QString highPressure)
{
QSqlQuery query;
query.prepare("select * from hypertension where highPressure=?");
query.addBindValue(highPressure);
query.exec();
//query.next();
struct hypertensionstruct p;
p.HPid=query.value(0).toInt();
p.Uid=query.value(1).toInt();
p.highPressure=query.value(2).toString();
p.lowPressure=query.value(3).toString();
return p;
}

struct userstruct
{int Uid;
QString Uname;
};

struct userstruct users::selectusers(QString name)
{
QSqlQuery query;
query.prepare("select * from users where Uname=?");
query.addBindValue(name);
query.exec();
query.next();
struct userstruct p;
p.Uid=query.value(0).toInt();
p.Uname=query.value(1).toString();
return p;
}

离线wxj120bw

只看该作者 3楼发表于: 2011-08-01

回 2楼(zq123456) 的帖子

selecthypertension函数,selectusers函数再贴下

离线zq123456

只看该作者 2楼发表于: 2011-08-01

query.exec(QObject::tr("create table users (Uid int primary key,"
"Uname varchar(10))"));
query.exec(QObject::tr("insert into users values(0,'katy')"));
query.exec(QObject::tr("insert into users values(1,'cindy')"));
query.exec(QObject::tr("insert into users values(2,'小王')"));

query.exec(QObject::tr("create table hypertension (HPid int primary key,"
"Uid int,"
"highPressure varchar(10) not null,"
"lowPressure varchar(10) not null)"));
query.exec(QObject::tr("insert into hypertension values(1,1,'10','20')"));

void Widget::on_pushButton_clicked()
{
QSqlQuery query;
QString name=(ui->lineEdit->text());
struct userstruct id=us->selectusers(name);
qDebug()<<id.Uid<<id.Uname;
}
void Widget::on_pushButton_2_clicked()
{
QSqlQuery query;
QString name=(ui->lineEdit_2->text());
struct hypertensionstruct id=us->selecthypertension(name);
qDebug()<<id.HPid<<id.Uid<<id.highPressure<<id.lowPressure;
}

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离线wxj120bw

只看该作者 1楼发表于: 2011-07-31

回楼主(zq123456) 的帖子

用[code][/code]编辑下你的代码还有打印下你界面的内容和sql语句