Most efficient way to iterate through a QSqlQuery result set?
I figured out how to improve the speed of iterating through the results. I had forgotten that I needed to first prepare the sql before executing and setForwardOnly
must be set to true.
QSqlQuery * query = new QSqlQuery(db);
query->setForwardOnly(true);
query->exec("SELECT [UserName]"
" FROM [dbo].[Users]");
Cameron Tinker
I am a Computer Science graduate from LSU. I enjoy programming computers, playing piano, and playing classic video games in my spare time. Professionally, I am a full stack web developer specializing in ASP.NET MVC and ASP.NET Web API single page applications. I am well versed in C# and .NET. I enjoy learning new technologies and keeping up with the latest in the software development industry.
Updated on June 14, 2022Comments
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Cameron Tinker almost 2 years
I'm querying a remote MSSQL Server database using QODBC and I have a result set returned but it appears as though it sends a query to SQL Server for each record one by one. This is really slow for iterating a result set. Running the query from Qt, it takes roughly 15 seconds to complete. I ran the same query in SQL Server Management Studio and it takes 1 second to return results. Here's the code I'm using:
QString connectionTemplate = "DRIVER={SQL SERVER};SERVER=server;DATABASE=db;"; QSqlDatabase db = QSqlDatabase::addDatabase("QODBC3", "db"); db.setDatabaseName(connectionTemplate); db.setUserName("user"); db.setPassword("password"); if (db.open()) { qDebug() << "OK!"; QSqlQuery * query = new QSqlQuery(db); query->exec("SELECT [UserName]" " FROM [dbo].[Users]"); while(query->next()) { QString userName = query->value(0).toString(); qDebug() << userName; } db.close(); } else { qDebug() << db.lastError().text(); }
Is there any way to capture the entire result set into memory and loop through it in memory? I'd rather not have the application take so long to iterate through a result set.