CODEWITHSUNDEEP
c++mysqlqt
goGud
goGud

Reputation: 4341

How to get database size with Qt?

I am trying to define my vector size with mysql database size in qt c++. After I execute my commands it returns 0 and get an error;

QMYSQLResult::data: column 1 out of range

in line: 

int dbSize = query.value(1).toInt();

However when I execute sql command in mysql-workbench it says 15

Here is my code blocks for get database size : 

int databaseConn::getDbSize()
{
    QSqlDatabase::database().transaction();
    QSqlQuery query;

    query.prepare("SELECT count(*) FROM images");
    query.exec();
    query.next();

    if( query.lastError().isValid())
    {
        qDebug() << query.lastError().text();
        QSqlDatabase::database().rollback();

        return -1;
    }
    else
    {
        int dbSize = query.value(1).toInt();

        qDebug() << dbSize;

        return dbSize;
    }
}

Could you please help me where is my mistake?

PS: I dont want to call whole db and count it like : 

QSqlQuery query("SELECT * FROM test");

query.record().count();

Upvotes: 1

Views: 653

Answers (1)

Amartel
Amartel

Reputation: 4286

index in QVariant QSqlQuery::value ( int index ) const means zero-based index of field in the select statement. In your case, the only field count(*) will have index 0:

int dbSize = query.value(0).toInt();

You can get fields' count from QSqlRecord:

qDebug() << query.record().count();

Upvotes: 2

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