Differences between database Objects

[ruben.rodrigues]

Hi all!

I am doing an application that for now connects to a mysql database but in the future should connect to oracle and msql (odbc). We want to have the database classes as plugins, that meaning 1 plugin per database capability.

My question is if after I have the QSqlQuery object the syntax is the same for all kinds of databases.

For example, if I do the implementation to the mysql class, after doing the query I could return it to the main class and it will handle the data from there.

MySql:

QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL"); //select database type
db.setHostName(_hostName);
db.setDatabaseName(_databaseName);
db.setUserName(_userName);
db.setUserName(_userPassword);
 
QSqlQuery query("USE " + _table);
query.exec("Select * from "+ _table);
//then put the query inside a QByteArray and return it to the class that has called it.
return qbytearray;

QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL"); //select database type
db.setHostName(_hostName);
db.setDatabaseName(_databaseName);
db.setUserName(_userName);
db.setUserName(_userPassword);

QSqlQuery query("USE " + _table);
query.exec("Select * from "+ _table);
//then put the query inside a QByteArray and return it to the class that has called it.
return qbytearray;

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then the class that has called it opens the QSqlQuery object and get the information.

//open qbytearray and read the QSqlQuery
while (query.next()) {
           QSqlRecord record = query.record();
           loginName = query.value(0).toString();
           loginPassword = query.value(1).toString();
           firstName = query.value(2).toString();
           surname = query.value(3).toString();
           phone = query.value(4).toString();
           email = query.value(5).toString();
}

//open qbytearray and read the QSqlQuery
while (query.next()) {
           QSqlRecord record = query.record();
           loginName = query.value(0).toString();
           loginPassword = query.value(1).toString();
           firstName = query.value(2).toString();
           surname = query.value(3).toString();
           phone = query.value(4).toString();
           email = query.value(5).toString();
}

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Does this syntax work for all database types?

Thanks

[Lykurg]

Try it, and it will work for all databases if they understand SQL. Also it is better to name the fields instead of using '*'.

And

QSqlQuery query("USE " + _table);
query.exec("Select * from "+ _table);

QSqlQuery query("USE " + _table);
query.exec("Select * from "+ _table);

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looks odd. It should be

USE mydatabase;
SELECT `id` FROM mytable;

USE mydatabase;
SELECT `id` FROM mytable;

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