Question

我一直在使用这种方式执行SQL查询，但是对于LIKE来说，它不起作用，我不知道为什么。任何想法？错误消息显示QSqlError（“”，“参数计数不匹配”，“”）。谢谢。

void MainWindow::on_searcButton_clicked()
{
    Login user;
    dbConnect db;
    if (!db.dbOpen()){
         qDebug()<<"DB not found";
    }
    QSqlQuery query;
    QString search=ui->searchEdit->text();
    qDebug()<<"Search: "<<search;
    query.prepare("select ID,Name from BOOKS where ((Name LIKE :search%) or (ID LIKE :search%)) where UserName=:user;");
    query.bindValue(":search",search);
    query.bindValue(":user",user.userLogOn);
    if(!query.exec()){
        qDebug()<<"Query error: "<<query.lastError();
    }
    QSqlQueryModel *modal =new QSqlQueryModel();
    modal->setQuery(query);
    qDebug()<<modal->rowCount();
    ui->bookList->setModel(modal);
    //db.dbClose();

}

Answer 1

这时候您可能已经解决了问题，但这是我的解决方案：

QSqlQuery query;

query.prepare(QString("SELECT field1, field2, field3 "
                      "FROM table1 "
                      "WHERE %1 LIKE :search_string ").arg(someComboBox->currentText()));
// With QString::arg() you could use a combobox to select the field 
// or any widget that you prefer.
// You can also use ILIKE Postgresql sentence for case insensitive

// Note that QSqlQuery::bindValue() is only for incoming values, not for replace fields, 
// that's the reason why you need to use QString::arg() to replace the search field.   
query.bindValue(":search_string", ("%" + searchLineEdit->text() + "%"));
// No need to use the SQL single quotes at the sides of percentage character ('%string%')

// This portion of code is useful to debug your query.
if(!query.exec()) {
   qDebug() << "Error in query, it happened: " + query.lastError().text();
   qDebug() << "The SQL text was: " << query.lastQuery().toUtf8;
}

// And if you need to watch your bound values, use this:    
qDebug() << queryForModel.boundValue(0).toString();

// Here's a bonus to see the results.
QSqlQueryModel *model = new QSqlQueryModel;
model->setQuery(query);

someTableView->setModel(model);

Answer 2

尝试一下

search = "%"+search+"%";
    query.prepare("select ID,Name from BOOKS where ((Name LIKE :search) or (ID LIKE :search)) where UserName=:user");

Qt SQL LIKE语句返回错误

2 个答案: