I try to get primaryKey programmatically and convert it to col name. this function not work as mast be.
QString getPrimaryFiled( const QString &tableName )
{
QSqlDatabase m_SqlDataBase = QSqlDatabase::database(StaticConnection::getDatabaseConnectionName());
return m_SqlDataBase.primaryIndex( tableName ).name();
}
But I can't find way to make it work, It's give me blank string
You are misusing the following method:
QSqlDatabase QSqlDatabase::database(const QString & connectionName = QLatin1String( defaultConnection ), bool open = true) [static]
Returns the database connection called connectionName. The database connection must have been previously added with addDatabase(). If open is true (the default) and the database connection is not already open it is opened now. If no connectionName is specified the default connection is used. If connectionName does not exist in the list of databases, an invalid connection is returned.
You should have written this:
QSqlDatabase m_SqlDataBase = QSqlDatabase::database( StaticConnection::getDatabaseConnectionName() );
Provided that you followed the documentation properly about addDatabase().
Related
I need to populate a QTableView by retrieving data from a QSqlTableModel object. I use following commands to make a connection to a sql server database:
QSqlDatabase db = QSqlDatabase::addDatabase("QODBC");
QString connectionTemplate = "DRIVER={SQL Native Client};SERVER=%1;DATABASE=%2;Uid=username;Pwd=password;Trusted_Connection=Yes;";
QString connectionString = connectionTemplate.arg("localhost").arg("mydb");
db.setDatabaseName(connectionString);
I validate the database connection by the methods isValid() and open() from QSqlDatabase class. I am also able to query from the database tables properly. ٍEvery thing is ok so far. But the problem arises when I use following commands:
QSqlTableModel* model = new QSqlTableModel(parent,db);
model->setTable("mytable");
qDebug() << model->lastError().text(); // the error message is printed on consul.
The method setTable not working and causes an error: Unable to find table \"mytable\".
I found the solution. I should open the database right after setDatabaseName and before creation of QSqlTableModel:
QSqlDatabase db = QSqlDatabase::addDatabase("QODBC");
QString connectionTemplate = "DRIVER={SQL Native Client};SERVER=%1;DATABASE=%2;Uid=username;Pwd=password;Trusted_Connection=Yes;";
QString connectionString = connectionTemplate.arg("localhost").arg("mydb");
db.setDatabaseName(connectionString);
db.open(); // :)
QSqlTableModel* model = new QSqlTableModel(parent,db);
model->setTable("mytable");
According to http://doc.qt.io/qt-5/qsqltablemodel.html#QSqlTableModel
the constructor of QSqlTablemodel:
Creates an empty QSqlTableModel and sets the parent to parent and the
database connection to db. If db is not valid, the default database
connection will be used.
In the event that your db object is not valid you would connect to a default database where your table is not available.
Double check the parameters used to initialize and setup QSqlDatabase db.
Using C++ Qt framework and sql server 2008 I've been trying to insert a record into a table with an identity field and retrieve the identity value. Below is a simplified code sample which actually does do the insert but just doesn't retreive the identity. The identity returned from query.value(0) is an invalid QVariant.
QSqlQuery query(*pConn);
query.prepare("insert into [VH_MANUFACTURER] values ('sRRS test man code','RRS type','RRS logo file',1,'RRS SEO para','RRS description','RS');"
"select SCOPE_IDENTITY();");
if(query.exec())
{
if(query.next())
{
QVariant identity = query.value(0);
int id=identity.toInt();
}
}
I've tried using select ##identity instead of scope_identity with no improvement and also QSqlQuery .lastInsertId() which also returns an invalid QVariant, see below.
bool bFeature = pConn->driver()->hasFeature(QSqlDriver::LastInsertId);
QSqlQuery query(*pConn);
query.prepare("insert into [VH_MANUFACTURER] ([MFG_NAME],[MFG_TYPE],[MFG_LOGO],[MFG_ACTIVE],[MFG_SEO_CONTENT],[MFG_DESCRI],[MFG_CAPMANCODE]) values ('sRRS test man code','RRS type','RRS logo file',1,'RRS SEO para','RRS description','RS')");
if(query.exec())
{
QVariant id=query.lastInsertId();
}
hasFeature returns true, so the driver is supposed to support what I'm trying to do.
Just to test the sql , I ran the sql directly through Sql Server Management Studio and it inserts as expected and returns the identity value correctly.
Finally found a work around using OUTPUT clause in sql. I don't exactly know why the other methods I tried don't work. There is a sql server bug associated with this feature but that doesn't explain why it worked in ssms but not in c++ Qt code. The sample below show's the work around. Here's the reference I used to solve this.
bool bFeature = pConn->driver()->hasFeature(QSqlDriver::LastInsertId);
QSqlQuery query(*pConn);
query.prepare("insert into [VH_MANUFACTURER] ([MFG_NAME],[MFG_TYPE],[MFG_LOGO],[MFG_ACTIVE],[MFG_SEO_CONTENT],[MFG_DESCRI],[MFG_CAPMANCODE]) OUTPUT INSERTED.MFG_ID values ('sRRS test man code','RRS type','RRS logo file',1,'RRS SEO para','RRS description','RS')");
if(query.exec())
{
if(query.next())
{
QVariant id=query.value("MFG_ID");
}
}
I am trying to use QSqlQueryModel in order to retrieve some values from my database like such:
QSqlDatabase db = QSqlDatabase::addDatabase("QPSQL", "test1");
db.setHostName(Vars::strDbHost);
db.setDatabaseName(Vars::strDbName);
db.setPort(Vars::strDbPort);
db.setUserName(Vars::strDbUsername);
db.setPassword(Vars::strDbPassword);
db.open()
QSqlQueryModel model;
model.setQuery(QString("SELECT * FROM users WHERE login=%2").arg(Vars::strUserLogin));
But I keep getting a QSqlQuery::exec: database not open error.
Why is this, and how can I correctly use QSqlQueryModel to retrieve the values I want?
You are calling the wrong version of setQuery. This only works with db which have the default name. In your case, you need to call void QSqlQueryModel::setQuery(const QString &query, const QSqlDatabase &db):
model.setQuery(QString("SELECT * FROM users WHERE login=%2").arg(Vars::strUserLogin)
, db);
i'm trying to connect to a sql database with the Qt-Framework.
Unfortunately db.open() always returns true (you can set any password, hostname, etc...), despite no connection is established(?). I derive that from the query not having any effect on the database.
I'm using LAMPP on Ubuntu 14.04.
I've got the following code:
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QApplication>
#include <QSql>
#include <QSqlDatabase>
#include <QMessageBox>
#include <QSqlQuery>
void MainWindow::on_ButtonSQL_clicked()
{
QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE", "con1");
db.setHostName("localhost");
db.setDatabaseName("kinectshop2015");
db.setUserName("root");
db.setPassword("");
QMessageBox msgBox;
if (db.open()) {
msgBox.setText("Yay! Your database host is "+db.hostName()+" .\n"+" The name of the database is "+db.databaseName()+".");
msgBox.exec();
}
QSqlQuery query;
query.exec("INSERT INTO users (id, username, balance, isAdmin)" "VALUES(3, 'somebody', 10000, 1)");
}
One problem is that you are specifying a connectionName.
QSqlDatabase QSqlDatabase::addDatabase(const QString & type, const QString & connectionName = QLatin1String( defaultConnection ))
If connectionName is not specified, the new connection becomes the default connection
Given that your db connection is not the default connection, you need to tell the QSqlQuery which db to use, i.e.
QSqlQuery query(db);
query.exec("INSERT INTO users (id, username, balance, isAdmin)" "VALUES(3, 'somebody', 10000, 1)");
The other 'problem' is that with sqlite you always create a new database by the call you are making, thus the problem is not that the DB is not open but that its contents are not right (since it will be empty if you specify a non existing filename). If I take your code and add
qDebug() << query.lastError();
after the query.exec it rightfully complains that
QSqlError(1, "Unable to execute statement", "no such table: users")
If I include a statement to create the table before the insert query
QSqlQuery createTable("create table users ( id INTEGER, username TEXT, balance REAL, isAdmin INTEGER)",db);
createTable.exec();
I correctly get the table in the newly create db file and it has the entry that you are trying to insert.
Does this help?
Here is what solved my problem. I used the driver QMYSQL instead of QSQLITE. I had only used the latter, because the first one couldn't be loaded. On Ubuntu & QT5 simply type sudo apt-get install libqt5sql5-mysql to resolve the problem.
I have recently begun working with QT and I'm having a small issue. I cant seem to understand how QVariant works. I've been going through the help and looking online but it is just not sinking in. In my project i am trying to populate a combo box with a list of manufacturers from a database. I have opened the database and pulled out the entries but I rename them all manValue. Now I understand why this is happening, the problem is I do not understand how to properly use QVariant to get the result I want. Originally i thought "manValue" was going to be the identifier for the string that held the actual value from the database but instead it reads the value from the database and makes sure it is not null, and then renames it. I already tried making a string before I assign the QVariant with any properties and assigning it the text i received from the database, and then inserting that string where manValue is but still no luck. Any help would be greatly appreciated. Sorry, I know this is going to be simple I'm just a noob and the help docs often confuse me.
QSqlDatabase db = QSqlDatabase::addDatabase("QODBC");
db.setHostName("LOCALHOST\\TestERPServer");
db.setDatabaseName("TestERPConnection");
if (db.open())
{
QMessageBox::information(this,"Connected","Connection to the Database was Established\n"
"\nStatus: Connected");
QSqlQuery mfrQry;
if (mfrQry.exec("SELECT * FROM erp_data.manufacturers;"))
{
if (mfrQry.value(1) == "")
{
QMessageBox::information(this,"No Connection","Nothing in the Manufacturer Database\n"
"\nError: " + db.lastError().text());
}
else
{
while (mfrQry.next())
{
ui->mfrComboBox->addItem("manValue",QVariant(mfrQry.value(1)));
}
}
}
else
{
QMessageBox::information(this,"No Connection","Connection to the Manufacturer Database could not be Established\n"
"\nError: " + db.lastError().text());
}
}
else
{
QMessageBox::information(this,"No Connection","Connection to the Database could not be Established\n"
"\nError: " + db.lastError().text());
}
The first problem in the provided code has to do with the way you manipulate the QSqlQuery.
Successfully executed SQL statements set the query's state to active
so that isActive() returns true. Otherwise the query's state is set to
inactive. In either case, when executing a new SQL statement, the
query is positioned on an invalid record. An active query must be
navigated to a valid record before values can be retrieved.
In order to move to a valid record you have to use one of the following:
next()
previous()
first()
last()
seek()
Once you are on a valid record you have to use the value() function in order to take the column you want. The returned value is QVariant so you need to convert to the desired type using one of the many toSomething functions QVariant provides.
So in your case the code should look like this:
QSqlQuery mfrQry;
if (mfrQry.exec("SELECT * FROM erp_data.manufacturers;"))
{
// This will loop through all records returned by the query
while (mfrQry.next()) {
// mfrQry.value(COLID) returns a QVariant containing the data of the current
// record in column COLID.
// Using toString we convert it to String
QString stringValue = mfrQry.value(COLID).toString();
// Now handle the QString the way you want...
}
}