So how to write the part of login to the database with the sql command .

[wter27]

QString var_s_user,var_s_pass,var_s_sql;
            var_s_user=ui->lineEdit_user->text().trimmed();
            var_s_pass=ui->lineEdit_pass->text().trimmed();
            QSqlQuery query_cmd;
            var_s_sql="select username from user where username = " +var_s_user + " and password="+var_s_pass+";";
            query_cmd.exec(var_s_sql);

QString var_s_user,var_s_pass,var_s_sql;
            var_s_user=ui->lineEdit_user->text().trimmed();
            var_s_pass=ui->lineEdit_pass->text().trimmed();
            QSqlQuery query_cmd;
            var_s_sql="select username from user where username = " +var_s_user + " and password="+var_s_pass+";";
            query_cmd.exec(var_s_sql);

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I have finished the connection to the database .And it could connect to the data normally.
But I just cant solve the login part.So how to check if the username and password is right.
I use the code QSqlRecord rec = query_cmd.record();to find out if there is a right username and password in the database.But it did not work .So anyone could give me some examples?

[mcosta]

When you use SELECT you must use QSqlQuery::next() to retreive records

QSqlQuery query_cmd("select username from user where username = " 
                                 + var_s_user + " and password="+var_s_pass);
if (query_cmd.next()) {
// Data found
}

QSqlQuery query_cmd("select username from user where username = " 
                                 + var_s_user + " and password="+var_s_pass);
if (query_cmd.next()) {
// Data found
}

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IN this case you can use QSqlQuery::first() instead of QSqlQuery::next() because you are intersted only on the presence of one record

[wter27]

thankyou very much.If there is only the way you just mentioned .I am glad to hear that.

[kornicameister]

I've got a question ?
Why do you need checking the correction of username and pass ?
I am just asking, because this thought is literally piercing through my brain and I can stop myself from asking