QSqlQuery insert full struct instead of individual fields? - c++

Question

Following QSqlQuery Class documentation one can implemented an insert operation in a MySQL database, i.e. like this:
QSqlQuery query;
query.prepare("INSERT INTO person (id, forename, surname) "
"VALUES (:id, :forename, :surname)");
query.bindValue(":id", 1001);
query.bindValue(":forename", "Bart");
query.bindValue(":surname", "Simpson");
query.exec();
It works. But it's fragile, isn't? It will stop working (because names are hard coded) when a column name mismatch occurs, if the database programmer changes a column name in the MySQL script, i.e. surname to lastname.
What came to my mind was to change the whole mechanism so that instead of inserting individual fields one big object (perhaps a struct composed by the individual fields) should be inserted. And then, in the db side, the fields should be split back into a set of fields, i.e. using a view or a trigger.
Am I going in the right direction?
I'll appreciate general comments on the issue.

Answer 1

Well, there is a way, but you must be sure that structure of the table and column meaning wouldn't change and your query has data of each column to insert.
Firstly, you must select all information about your table:
SELECT c.column_name FROM information_schema.columns c
WHERE c.table_name = 'some_table_name'
ORDER BY c.ordinal_position ASC
Secondly, your code can be change like this. I am using universal method that meaning you have already known data:
QList<QVariant> valuesList { QVariant(1), QVariant("Bart"), QVariant("Simpson") };
QList<QPair<QString, QVariant>> varList;
QSqlQuery query;
query.exec("SELECT #rownum := #rownum + 1 AS row_num, c.column_name
FROM information_schema.columns c, (SELECT #rownum := -1) r
WHERE c.table_name = 'some_table_name'
ORDER BY c.ordinal_position ASC");
while(query.next())
colList << QPair<QString, QString>(query.value(1).toString(),
valuesList.at(query.value(0).toInt()));
QString queryString = "INSERT INTO person (%1) "
"VALUES (%2)";
QString insertColsString;
QString bindColsString;
for(int i = 0; i < colList.size(); i++) {
insertColsString += colList.at(i).first + ", ";
bindColsString += ":" colList.at(i).first + ", ";
}
if(!insertColsString.isEmpty()) {
insertColsString.chop(2);
bindColsString.chop(2);
}
query.prepare(queryString.arg(insertColsString, bindColsString));
for(int i = 0; i < colList.size(); i++)
query.bindValue(":" + colList.at(i).first, colList.at(i).second);
query.exec();