Data file and QSql

Guys,

l would like to use a QSQL database to load and process large data files...but l'm very new to QSQL( but know pretty well Qt) and before to spend my nights on it l would like to get a few advises.

my files have the following format

Field1 Field2 Field3 Field4 Field5 ....
1 12 25 251 1255
1 14 21 432 1254
1 12 22 435 1252
2 18 23 134 1258
2 17 25 251 1259
2 19 24 250 1252
3 11 26 251 1254
3 19 25 251 1255
3 17 21 251 1256
...

l would to store this data in a database, and access it with some sort of filter to select the rows with specific value of Field2,3, 4...

well, just a basic database l guess... is anyone can give me the inspiration ?

regards,

Michael

Here's what I would do.

1. Create a struct to hold the fields.
   
   Example:
   
   struct fields {
   int field1;
   int field2;
   int field3;
   int field4;
   int field5;
   };

1. Create a list based on the above struct.
   
   Like this: QList<fields *> fieldList;

1. Parse the datafile. Read each line and split the line based on the space character.
   Create a new fields element and add the data.
   
   Example:
   
   QFile file("yourfilename");
   file.open(...);
   
   while (!file.atEnd()) {
   QString line = file.readLine();
   QStringList fields = line.split(" ");
   fields *newFields = new fields;
   foreach(QString field, fields) {
   newFields->field1 = fields.at(0).toInt();
   ...
   }
   fieldList.append(newFields);
   }

1. When done parsing the file, use the fieldList to add the data to the database, but first create the database.
   
   Here's how you create a simple SQLite database:
   
   QSqlDatabase database = QSqlDatabase::addDatabase("QSQLite", "fieldsdb");
   database.setHostname("localhost");
   database.setDatabaseName("./fields.db");
   database.open();
   
   QString queryString;
   queryString = "CREATE TABLE fields (";
   queryString += " fieldId INTEGER PRIMARY KEY,";
   queryString += " field1 INTEGER,";
   ...
   queryString += "field 5 INTEGER)";
   
   QSqlQuery createQuery(QSqlDatabase::database("fieldsdb"));
   createQuery.exec(queryString);

1. Add the data to the database, like this:
   
   database.transaction();
   
   QSqlQuery queryAddField(QSqlDatabase::database("fieldsdb"));
   queryAddField.prepare("INSERT INTO fields (field1, field2, field3, field4, field5) VALUES (?,?,?,?,?)");
   
   foreach(Fields *field, fieldList) {
   queryAddField.addBindValue(field->field1);
   ...
   queryAddField.addBindValue(field->field5);
   queryAddField.exec();
   }
   
   database.commit();

That should do it.

When you want to read from the database, create a new QSqlQuery with the query SELECT * FROM fields WHERE field5 = 5
This will give all rows and columns where field5 equals 5.
For more information see: http://www.w3schools.com/sql/default.asp
And the Qt documentation.

thanks a lot ... you gave me more than l was hoping, l will look into it.

thanks again,

Michael

I would use the model / record architecture. Much less programming. See docs QSqlQueryModel and QSqlRecord classes.