Qt C++中Combobox如何获取当前文本对应的DepartmentTbl表ID值

推荐方案（最优）：初始化ComboBox时预绑定部门ID #

这种方案不需要每次提交时额外查询数据库，性能更高，逻辑也更稳妥。

• 第一步：修改你填充DepartmentCombo的代码，在添加部门名称时同步把对应的部门ID存入Item的用户数据域
  示例填充代码：

// 你填充部门下拉框的逻辑位置，比如窗口构造函数/init函数里
QSqlQuery deptQry;
deptQry.exec("SELECT DepartmentID, DepartmentName FROM DepartmentTbl");
while(deptQry.next()) {
    int deptId = deptQry.value(0).toInt();
    QString deptName = deptQry.value(1).toString();
    // 第二个参数就是存入的用户数据，存部门ID
    ui->DepartmentCombo->addItem(deptName, deptId);
}

• 第二步：修改你现有槽函数里的取值逻辑，直接取预存的ID即可
  修改后的槽函数代码：

void addteacherform::on_newTeacherButton_clicked()
{
    dbRepository dr;
    dr.OpenDBConnection();

    //retrieve data from field
    QString fname = ui->firstnameEdit->text();
    QString mname = ui->middleIEdit->text();
    QString lname = ui->lastnameEdit->text();
    // 替换原来的currentText取值，直接拿预存的部门ID
    int departmentId = ui->DepartmentCombo->currentData().toInt(); 

    //insert query
    QSqlQuery qry1;
    qry1.prepare("INSERT INTO InstructorTbl (InsFname, InsMname, InsLname, DepartmentID)"
                "VALUES (:InsFname, :InsMname, :InsLname,:DepartmentID)");
    qry1.bindValue(":InsFname",fname);
    qry1.bindValue(":InsMname",mname);
    qry1.bindValue(":InsLname",lname);
    qry1.bindValue(":DepartmentID",departmentId);

    if(qry1.exec()){
          QMessageBox::information(this,"Added", "Data Added Successfully");
       }
    else{
           qDebug() << "add data failed: " << qry1.lastError();
        }
     dr.CloseDBConnection();
}

应急方案：提交时临时查询数据库获取ID #

如果你不方便修改下拉框初始化逻辑，可以用这种方案，缺点是会多一次数据库查询，且如果部门名称重复会有匹配错误问题：

void addteacherform::on_newTeacherButton_clicked()
{
    dbRepository dr;
    dr.OpenDBConnection();

    //retrieve data from field
    QString fname = ui->firstnameEdit->text();
    QString mname = ui->middleIEdit->text();
    QString lname = ui->lastnameEdit->text();
    QString deptName = ui->DepartmentCombo->currentText(); 

    // 先查部门表拿对应ID
    QSqlQuery deptQry;
    deptQry.prepare("SELECT DepartmentID FROM DepartmentTbl WHERE DepartmentName = :deptName");
    deptQry.bindValue(":deptName", deptName);
    int departmentId = 0;
    if(deptQry.exec() && deptQry.next()) {
        departmentId = deptQry.value(0).toInt();
    } else {
        qDebug() << "查询部门ID失败：" << deptQry.lastError();
        dr.CloseDBConnection();
        return;
    }

    //insert query
    QSqlQuery qry1;
    qry1.prepare("INSERT INTO InstructorTbl (InsFname, InsMname, InsLname, DepartmentID)"
                "VALUES (:InsFname, :InsMname, :InsLname,:DepartmentID)");
    qry1.bindValue(":InsFname",fname);
    qry1.bindValue(":InsMname",mname);
    qry1.bindValue(":InsLname",lname);
    qry1.bindValue(":DepartmentID",departmentId);

    if(qry1.exec()){
          QMessageBox::information(this,"Added", "Data Added Successfully");
       }
    else{
           qDebug() << "add data failed: " << qry1.lastError();
        }
     dr.CloseDBConnection();
}

• 请把代码中的DepartmentID、DepartmentName字段名替换为你自己DepartmentTbl表中实际的字段名
• 如果部门名称存在重复的情况，必须用第一种预绑定ID的方案，否则会出现匹配错误

内容的提问来源于stack exchange，提问作者Clariss