Qt5 从 MySQL 数据库中选择数据

qt5 selecting data from mysql database

本文关键字：选择 数据 数据库 MySQL Qt5      更新时间：2023-10-16

我想建立一个登录系统，我有mysql数据库我想根据我的mysql数据库用户名和密码登录，但它不起作用，我想我的代码有问题，请检查代码

void MainWindow::on_loginBtn_clicked()
{
QSqlDatabase db;
db = QSqlDatabase::addDatabase("QMYSQL", "MyConnect");
db.setHostName("localhost");
db.setUserName("root");
db.setPassword("");
db.setDatabaseName("qtregister");
QString username = ui->loginEdit->text();
QString password = ui->loginPassword->text();

if(db.open()) {
QSqlQuery query(QSqlDatabase::database("MyConnect"));
query.prepare(QString("SELECT username and password from users where username = :username AND password = :password"));
query.bindValue(":username", username);
query.bindValue(":password", password);
if(!query.exec()) {
QMessageBox::information(this, "Failed", "Failed To Login");
}else {
QMessageBox::information(this, "Success", "Login Success");
}
}
else {
QMessageBox::information(this, "Not Connected", "Not Conneced Success");
}
}

更新

您的查询中存在错误 (有时您需要在Qt(如mysql clis或在线环境(中调试查询 http://sqlfiddle.com(

SELECT username,password from users where username = :username AND password = :password

而不是

SELECT username and password from users where username = :username AND password = :password

更正的答案

void MainWindow::on_loginBtn_clicked() {
QSqlDatabase db;
db = QSqlDatabase::addDatabase("QMYSQL", "MyConnect");
db.setHostName("localhost");
db.setUserName("root");
db.setPassword("");
db.setDatabaseName("qtregister");
QString username = ui - > loginEdit - > text();
QString password = ui - > loginPassword - > text();
if (db.open()) {
QSqlQuery query(db);
query.prepare(QString("SELECT username , password from users where username = :username AND password = :password"));
query.bindValue(":username", username);
query.bindValue(":password", password);
if (!query.exec()) {
QMessageBox::information(this, "Failed", "Error in executing query");
} else {
while (query.next()) {
QString usernameFromDB = query.value(0).toString();
QString passwordFromDB = query.value(1).toString();
qDebug() << usernameFromDB << passwordFromDB;
if (usernameFromDB == username && passwordFromDB == password)
QMessageBox::information(this, "Success", "Login Success");
else
QMessageBox::information(this, "Failed", "Username or password error");
}
}
} else {
QMessageBox::information(this, "Not Connected", "Not Conneced Success");
}
}
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